@article{36701, abstract = {{Nowadays, mobility and transience are no longer exclusively associated with the marginalized and socially excluded, such as homeless or displaced people. On the contrary, mobility and transience have become a constitutive pattern of the highly skilled postmodern workforce. Yet, how mobile professionals negotiate the meaning of their homes in ‘liquid times’ and what homemaking practices they use to deal with the temporal uncertainty of their homes are questions that still require further research. This article – based on ethnographic research on German and American managers conducted in China, Germany and the United States between 2011 and 2014 – contributes to this research question by examining how mobile professionals make sense of the transience of their current homes and how transience is reflected in their homemaking practices. The article argues that for mobile professionals the home becomes a critical place not only because of new multilocal spatialities but also because of new transient temporalities. Due to the corporate practice of giving successive temporary contracts, the mobile managers’ everyday life is characterized by a ‘permanent provisionality’, that is, an incongruence of the initially imagined and the actual time horizons of their mobility. This article shows how this ‘permanent provisionality’ is worked into the material and social textures of expatriate homes.}}, author = {{Spiegel, Anna}}, issn = {{2397-7140}}, journal = {{Transitions: Journal of Transient Migration }}, number = {{2}}, pages = {{89--108}}, title = {{{Permanent provisionality: The homes of mobile managerial professionals between temporariness and permanence}}}, doi = {{https://doi.org/10.1386/tjtm_00034_1}}, volume = {{5}}, year = {{2021}}, } @article{25227, abstract = {{AbstractQuantum well (QW) heterostructures have been extensively used for the realization of a wide range of optical and electronic devices. Exploiting their potential for further improvement and development requires a fundamental understanding of their electronic structure. So far, the most commonly used experimental techniques for this purpose have been all-optical spectroscopy methods that, however, are generally averaging in momentum space. Additional information can be gained by angle-resolved photoelectron spectroscopy (ARPES), which measures the electronic structure with momentum resolution. Here we report on the use of extremely low-energy ARPES (photon energy ~ 7 eV) to increase depth sensitivity and access buried QW states, located at 3 nm and 6 nm below the surface of cubic-GaN/AlN and GaAs/AlGaAs heterostructures, respectively. We find that the QW states in cubic-GaN/AlN can indeed be observed, but not their energy dispersion, because of the high surface roughness. The GaAs/AlGaAs QW states, on the other hand, are buried too deep to be detected by extremely low-energy ARPES. Since the sample surface is much flatter, the ARPES spectra of the GaAs/AlGaAs show distinct features in momentum space, which can be reconducted to the band structure of the topmost surface layer of the QW structure. Our results provide important information about the samples’ properties required to perform extremely low-energy ARPES experiments on electronic states buried in semiconductor heterostructures.}}, author = {{Hajlaoui, Mahdi and Ponzoni, Stefano and Deppe, Michael and Henksmeier, Tobias and As, Donat Josef and Reuter, Dirk and Zentgraf, Thomas and Springholz, Gunther and Schneider, Claus Michael and Cramm, Stefan and Cinchetti, Mirko}}, issn = {{2045-2322}}, journal = {{Scientific Reports}}, title = {{{Extremely low-energy ARPES of quantum well states in cubic-GaN/AlN and GaAs/AlGaAs heterostructures}}}, doi = {{10.1038/s41598-021-98569-6}}, volume = {{11}}, year = {{2021}}, } @inproceedings{24000, author = {{Heitkaemper, Jens and Schmalenstroeer, Joerg and Ion, Valentin and Haeb-Umbach, Reinhold}}, booktitle = {{Speech Communication; 14th ITG-Symposium}}, pages = {{1--5}}, title = {{{A Database for Research on Detection and Enhancement of Speech Transmitted over HF links}}}, year = {{2021}}, } @article{45381, author = {{Dröse, Jennifer and Prediger, S. and Neugebauer, P. and Danhier, R. D. and Mertins, B.}}, journal = {{International Electronic Journal of Mathematics Education, 16(1), em0625}}, title = {{{Investigating students' processes of noticing and interpreting syntactic language features in word problem solving through eye-tracking}}}, doi = {{doi.org/10.29333/iejme/9674n }}, year = {{2021}}, } @article{45380, author = {{Dröse, Jennifer and Prediger, S.}}, journal = {{Studies in Educational Evaluation, 68 (100953)}}, pages = {{1--15}}, title = {{{Identifying obstacles is not enough for everybody – Differential efficacy of an intervention fostering fifth graders’ comprehension for word problems}}}, doi = {{doi.org/10.1016/j.stueduc.2020.100953}}, year = {{2021}}, } @article{22528, abstract = {{Due to the ad hoc nature of wireless acoustic sensor networks, the position of the sensor nodes is typically unknown. This contribution proposes a technique to estimate the position and orientation of the sensor nodes from the recorded speech signals. The method assumes that a node comprises a microphone array with synchronously sampled microphones rather than a single microphone, but does not require the sampling clocks of the nodes to be synchronized. From the observed audio signals, the distances between the acoustic sources and arrays, as well as the directions of arrival, are estimated. They serve as input to a non-linear least squares problem, from which both the sensor nodes’ positions and orientations, as well as the source positions, are alternatingly estimated in an iterative process. Given one set of unknowns, i.e., either the source positions or the sensor nodes’ geometry, the other set of unknowns can be computed in closed-form. The proposed approach is computationally efficient and the first one, which employs both distance and directional information for geometry calibration in a common cost function. Since both distance and direction of arrival measurements suffer from outliers, e.g., caused by strong reflections of the sound waves on the surfaces of the room, we introduce measures to deemphasize or remove unreliable measurements. Additionally, we discuss modifications of our previously proposed deep neural network-based acoustic distance estimator, to account not only for omnidirectional sources but also for directional sources. Simulation results show good positioning accuracy and compare very favorably with alternative approaches from the literature.}}, author = {{Gburrek, Tobias and Schmalenstroeer, Joerg and Haeb-Umbach, Reinhold}}, issn = {{1687-4722}}, journal = {{EURASIP Journal on Audio, Speech, and Music Processing}}, title = {{{Geometry calibration in wireless acoustic sensor networks utilizing DoA and distance information}}}, doi = {{10.1186/s13636-021-00210-x}}, year = {{2021}}, } @inproceedings{23994, author = {{Gburrek, Tobias and Schmalenstroeer, Joerg and Haeb-Umbach, Reinhold}}, booktitle = {{ICASSP 2021 - 2021 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)}}, title = {{{Iterative Geometry Calibration from Distance Estimates for Wireless Acoustic Sensor Networks}}}, doi = {{10.1109/icassp39728.2021.9413831}}, year = {{2021}}, } @inproceedings{23999, author = {{Gburrek, Tobias and Schmalenstroeer, Joerg and Haeb-Umbach, Reinhold}}, booktitle = {{Speech Communication; 14th ITG-Symposium}}, pages = {{1--5}}, title = {{{On Source-Microphone Distance Estimation Using Convolutional Recurrent Neural Networks}}}, year = {{2021}}, } @inproceedings{23997, author = {{Chinaev, Aleksej and Enzner, Gerald and Gburrek, Tobias and Schmalenstroeer, Joerg}}, booktitle = {{29th European Signal Processing Conference (EUSIPCO)}}, pages = {{1--5}}, title = {{{Online Estimation of Sampling Rate Offsets in Wireless Acoustic Sensor Networks with Packet Loss}}}, year = {{2021}}, } @inbook{49009, author = {{Moritz, Tilman}}, booktitle = {{Katholische Konfessionalisierung in Paderborn? Religiöse Prozesse in der Frühen Neuzeit}}, editor = {{Kopp, Stefan and Moritz, Tilman and Priesching, Nicole}}, location = {{Paderborn}}, pages = {{199 -- 239}}, publisher = {{Aschendorff}}, title = {{{Das Commentariolum Ferdinands von Fürstenberg – eine lateinisch-deutsche Synopse}}}, year = {{2021}}, } @inproceedings{29304, abstract = {{In this work we address disentanglement of style and content in speech signals. We propose a fully convolutional variational autoencoder employing two encoders: a content encoder and a style encoder. To foster disentanglement, we propose adversarial contrastive predictive coding. This new disentanglement method does neither need parallel data nor any supervision. We show that the proposed technique is capable of separating speaker and content traits into the two different representations and show competitive speaker-content disentanglement performance compared to other unsupervised approaches. We further demonstrate an increased robustness of the content representation against a train-test mismatch compared to spectral features, when used for phone recognition.}}, author = {{Ebbers, Janek and Kuhlmann, Michael and Cord-Landwehr, Tobias and Haeb-Umbach, Reinhold}}, booktitle = {{Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)}}, pages = {{3860–3864}}, title = {{{Contrastive Predictive Coding Supported Factorized Variational Autoencoder for Unsupervised Learning of Disentangled Speech Representations}}}, year = {{2021}}, } @inproceedings{22894, abstract = {{The first order optimality conditions of optimal control problems (OCPs) can be regarded as boundary value problems for Hamiltonian systems. Variational or symplectic discretisation methods are classically known for their excellent long term behaviour. As boundary value problems are posed on intervals of fixed, moderate length, it is not immediately clear whether methods can profit from structure preservation in this context. When parameters are present, solutions can undergo bifurcations, for instance, two solutions can merge and annihilate one another as parameters are varied. We will show that generic bifurcations of an OCP are preserved under discretisation when the OCP is either directly discretised to a discrete OCP (direct method) or translated into a Hamiltonian boundary value problem using first order necessary conditions of optimality which is then solved using a symplectic integrator (indirect method). Moreover, certain bifurcations break when a non-symplectic scheme is used. The general phenomenon is illustrated on the example of a cut locus of an ellipsoid.}}, author = {{Offen, Christian and Ober-Blöbaum, Sina}}, issn = {{2405-8963}}, keywords = {{optimal control, catastrophe theory, bifurcations, variational methods, symplectic integrators}}, location = {{Berlin, Germany}}, pages = {{334--339}}, title = {{{Bifurcation preserving discretisations of optimal control problems}}}, doi = {{https://doi.org/10.1016/j.ifacol.2021.11.099}}, volume = {{54(19)}}, year = {{2021}}, } @article{47963, abstract = {{Nonlinear and quantum optical devices based on periodically-poled thin film lithium niobate (PP-TFLN) have gained considerable interest lately, due to their significantly improved performance as compared to their bulk counterparts. Nevertheless, performance parameters such as conversion efficiency, minimum pump power, and spectral bandwidth strongly depend on the quality of the domain structure in these PP-TFLN samples, e.g., their homogeneity and duty cycle, as well as on the overlap and penetration depth of domains with the waveguide mode. Hence, in order to propose improved fabrication protocols, a profound quality control of domain structures is needed that allows quantifying and thoroughly analyzing these parameters. In this paper, we propose to combine a set of nanometer-to-micrometer-scale imaging techniques, i.e., piezoresponse force microscopy (PFM), second-harmonic generation (SHG), and Raman spectroscopy (RS), to access the relevant and crucial sample properties through cross-correlating these methods. Based on our findings, we designate SHG to be the best-suited standard imaging technique for this purpose, in particular when investigating the domain poling process in x-cut TFLNs. While PFM is excellently recommended for near-surface high-resolution imaging, RS provides thorough insights into stress and/or defect distributions, as associated with these domain structures. In this context, our work here indicates unexpectedly large signs for internal fields occurring in x-cut PP-TFLNs that are substantially larger as compared to previous observations in bulk LN.}}, author = {{Reitzig, Sven and Rüsing, Michael and Zhao, Jie and Kirbus, Benjamin and Mookherjea, Shayan and Eng, Lukas M.}}, issn = {{2073-4352}}, journal = {{Crystals}}, keywords = {{Inorganic Chemistry, Condensed Matter Physics, General Materials Science, General Chemical Engineering}}, number = {{3}}, publisher = {{MDPI AG}}, title = {{{“Seeing Is Believing”—In-Depth Analysis by Co-Imaging of Periodically-Poled X-Cut Lithium Niobate Thin Films}}}, doi = {{10.3390/cryst11030288}}, volume = {{11}}, year = {{2021}}, } @article{47964, abstract = {{In the last two decades, variably doped strontium barium niobate (SBN) has attracted a lot of scientific interest mainly due to its specific non-linear optical response. Comparably, the parental compound, i.e., undoped SBN, appears to be less studied so far. Here, two different cuts of single-crystalline nominally pure strontium barium niobate in the composition Sr0.61Ba0.39Nb2O6 (SBN61) are comprehensively studied and analyzed with regard to their photoconductive responses. We present conductance measurements under systematically varied illumination conditions along either the polar z-axis or perpendicular to it (x-cut). Apart from a pronounced photoconductance (PC) already under daylight and a large effect upon super-bandgap illumination in general, we observe (i) distinct spectral features when sweeping the excitation wavelength over the sub-bandgap region as then discussed in the context of deep and shallow trap states, (ii) extremely slow long-term relaxation for both light-on and light-off transients in the range of hours and days, (iii) a critical dependence of the photoresponse on the pre-illumination history of the sample, and (iv) a current–voltage hysteresis depending on both the illumination and the electrical-measurement conditions in a complex manner.}}, author = {{Beyreuther, Elke and Ratzenberger, Julius and Roeper, Matthias and Kirbus, Benjamin and Rüsing, Michael and Ivleva, Liudmila I. and Eng, Lukas M.}}, issn = {{2073-4352}}, journal = {{Crystals}}, keywords = {{Inorganic Chemistry, Condensed Matter Physics, General Materials Science, General Chemical Engineering}}, number = {{7}}, publisher = {{MDPI AG}}, title = {{{Photoconduction of Polar and Nonpolar Cuts of Undoped Sr0.61Ba0.39Nb2O6 Single Crystals}}}, doi = {{10.3390/cryst11070780}}, volume = {{11}}, year = {{2021}}, } @article{47965, abstract = {{Exceptionally electron-rich, nearly trigonal-planar tricyanidometalate anions [Fe(CN)3]7− and [Ru(CN)3]7− were stabilized in LiSr3[Fe(CN)3] and AE3.5[M(CN)3] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of −IV. Microcrystalline powders were obtained by a solid-state route, single crystals from alkali metal flux. While LiSr3[Fe(CN)3] crystallizes in P63/m, the polar space group P63 with three-fold cell volume for AE3.5[M(CN)3] is confirmed by second harmonic generation. X-ray diffraction, IR and Raman spectroscopy reveal longer C−N distances (124–128 pm) and much lower stretching frequencies (1484–1634 cm−1) than in classical cyanidometalates. Weak C−N bonds in combination with strong M−C π-bonding is a scheme also known for carbonylmetalates. Instead of the formal notation [Fe−IV(CN−)3]7−, quantum chemical calculations reveal non-innocent intermediate-valent CN1.67− ligands and a closed-shell d10 configuration for Fe, that is, Fe2−.}}, author = {{Jach, Franziska and Wagner, Frank R. and Amber, Zeeshan H. and Rüsing, Michael and Hunger, Jens and Prots, Yurii and Kaiser, Martin and Bobnar, Matej and Jesche, Anton and Eng, Lukas M. and Ruck, Michael and Höhn, Peter}}, issn = {{1433-7851}}, journal = {{Angewandte Chemie International Edition}}, keywords = {{General Chemistry, Catalysis}}, number = {{29}}, pages = {{15879--15885}}, publisher = {{Wiley}}, title = {{{Tricyanidoferrates(−IV) and Ruthenates(−IV) with Non‐Innocent Cyanido Ligands}}}, doi = {{10.1002/anie.202103268}}, volume = {{60}}, year = {{2021}}, } @article{47973, abstract = {{Thin-film lithium niobate (TFLN) in the form of x- or z-cut lithium-niobate-on-insulator has attracted considerable interest as a very promising and novel platform for developing integrated optoelectronic (nano)devices and exploring fundamental research. Here, we investigate the coherent interaction length lc of optical second-harmonic generation (SHG) microscopy in such samples, that are purposely prepared into a wedge shape, in order to elegantly tune the geometrical confinement from bulk thicknesses down to approximately 50 nm. SHG microscopy is a very powerful and non-invasive tool for the investigation of structural properties in the biological and solid-state sciences, especially for visualizing and analyzing ferroelectric domains and domain walls. However, unlike in bulk lithium niobate (LN), SHG microscopy in TFLN is impacted by interfacial reflections and resonant enhancement, both of which rely on film thickness and substrate material. In this paper, we show that the dominant SHG contribution measured on TFLN in backreflection is the co-propagating phase-matched SHG signal and not the counter-propagating SHG portion as is the case for bulk LN samples. Moreover, lc depends on the incident pump laser wavelength (sample dispersion) but also on the numerical aperture of the focussing objective in use. These experimental findings on x- and z-cut TFLN are excellently backed up by our advanced numerical simulations.}}, author = {{Amber, Zeeshan H. and Kirbus, Benjamin and Eng, Lukas M. and Rüsing, Michael}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{13}}, pages = {{133102}}, publisher = {{AIP Publishing}}, title = {{{Quantifying the coherent interaction length of second-harmonic microscopy in lithium niobate confined nanostructures}}}, doi = {{10.1063/5.0058996}}, volume = {{130}}, year = {{2021}}, } @article{47977, abstract = {{Orange-colored crystals of the oxoferrate tellurate K12+6xFe6Te4−xO27 [x=0.222(4)] were synthesized in a potassium hydroxide hydroflux with a molar water–base ratio n(H2O)/n(KOH) of 1.5 starting from Fe(NO3)3 ⋅ 9H2O, TeO2 and H2O2 at about 200 °C. By using (NH4)2TeO4 instead of TeO2, a fine powder consisting of microcrystalline spheres of K12+6xFe6Te4−xO27 was obtained. K12+6xFe6Te4−xO27 crystallizes in the acentric cubic space group Iurn:x-wiley:09476539:media:chem202102464:chem202102464-math-0001 3d. [FeIIIO5] pyramids share their apical atoms in [Fe2O9] groups and two of their edges with [TeVIO6] octahedra to form an open framework that consists of two loosely connected, but not interpenetrating, chiral networks. The flexibility of the hinged oxometalate network manifests in a piezoelectric response similar to that of LiNbO3.The potassium cations are mobile in channels that run along the <111> directions and cross in cavities acting as nodes. The ion conductivity of cold-pressed pellets of ball-milled K12+6xFe6Te4−xO27 is 2.3×10^(−4) S ⋅ cm^(−1) at room temperature. Magnetization measurements and neutron diffraction indicate antiferromagnetic coupling in the [Fe2O9] groups.}}, author = {{Albrecht, Ralf and Hoelzel, Markus and Beccard, Henrik and Rüsing, Michael and Eng, Lukas and Doert, Thomas and Ruck, Michael}}, issn = {{0947-6539}}, journal = {{Chemistry – A European Journal}}, keywords = {{General Chemistry, Catalysis, Organic Chemistry}}, number = {{57}}, pages = {{14299--14306}}, publisher = {{Wiley}}, title = {{{Potassium Ion Conductivity in the Cubic Labyrinth of a Piezoelectric, Antiferromagnetic Oxoferrate(III) Tellurate(VI)}}}, doi = {{10.1002/chem.202102464}}, volume = {{27}}, year = {{2021}}, } @article{47974, abstract = {{Domain walls (DWs) in ferroelectric (FE) and multiferroic materials possess an ever-growing potential as integrated functional elements, for instance in optoelectronic nanodevices. Mandatory, however, is the profound knowledge of the local-scale electronic and optical properties, especially at DWs that are still incompletely characterized to date. Here, we quantify the refractive index of individual FE DWs in periodically-poled LiNbO3 (PPLN) single crystals. When applying polarization-sensitive optical coherence tomography (PS-OCT) at 1300 nm using circular light polarization, we are able to probe the relevant electro-optical properties close to and at the DWs, including also their ordinary and extraordinary contributions. When comparing to numerical calculations, we conclude that the DW signals recorded for ordinary and extraordinary polarization stem from an increased refractive index of at least Δn > 2·10−3 that originates from a tiny region of < 30 nm in width. PS-OCT hence provides an extremely valuable tool to decipher and quantify subtle changes of refractive index profiles for both inorganic and biomedical nanomaterial systems.}}, author = {{Golde, Jonas and Rüsing, Michael and Rix, Jan and Eng, Lukas M. and Koch, Edmund}}, issn = {{1094-4087}}, journal = {{Optics Express}}, keywords = {{Atomic and Molecular Physics, and Optics}}, number = {{21}}, publisher = {{Optica Publishing Group}}, title = {{{Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO3 single crystals by polarization-sensitive optical coherence tomography}}}, doi = {{10.1364/oe.432810}}, volume = {{29}}, year = {{2021}}, } @article{47979, abstract = {{Broadband coherent anti-Stokes Raman scattering (B-CARS) has emerged in recent years as a promising chemosensitive high-speed imaging technique. B-CARS allows for the detection of vibrational sample properties in analogy to spontaneous Raman spectroscopy, but also makes electronic sample environments accessible due to its resonant excitation mechanism. Nevertheless, this technique has only gained interest in the biomedical field so far, whereas CARS investigations on solid-state materials are rare and concentrate on layered, two-dimensional materials such as graphene and hexagonal boron nitride . In this work, we discuss the specific properties of this technique when applied to single-crystalline samples, with respect to signal generation, phase matching, and selection rules in the model systems lithium niobate and lithium tantalate. Via polarized B-CARS measurements and subsequent phase retrieval, we validate the predicted selection rules, unequivocally assign the phonons of the A1(TO), E(TO) and A1(LO) branches to the detected CARS peaks, and address differences in spontaneous Raman spectroscopy concerning peak frequencies and scattering efficiencies. We thus establish this technique for future investigations of solid-state materials, specifically in the field of ferroelectric single crystals.}}, author = {{Hempel, Franz and Reitzig, Sven and Rüsing, Michael and Eng, Lukas M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{22}}, publisher = {{American Physical Society (APS)}}, title = {{{Broadband coherent anti-Stokes Raman scattering for crystalline materials}}}, doi = {{10.1103/physrevb.104.224308}}, volume = {{104}}, year = {{2021}}, } @article{34827, abstract = {{ZusammenfassungZu den ersten geometrischen Begriffen, die Kinder bereits im Elementar- und Primarbereich lernen, zählen u. a. Viereck, Rechteck und Quadrat. Studien zeigen, dass Lernende bereits früh individuelle Vorstellungen, sog. individuelle Begriffskonzepte, zu diesen Begriffen aufbauen. Zwar wird die Entwicklung von Begriffsverständnis in verschiedenen mathematikdidaktischen Stufenmodellen dargestellt, diese sind jedoch generisch und beschreiben nicht explizit die Entwicklung der ersten individuellen Begriffskonzepte von Lernenden zu Viereck, Rechteck und Quadrat. Aus empirischer Sicht liegen verschiedene Studien vor, die einzelne Aspekte der individuellen Begriffskonzepte von Lernenden unterschiedlicher Altersgruppen zu diesen Begriffen ausleuchten. Um Begriffsbildungsprozesse aus empirischer Sicht detaillierter entlang der jeweils vorherrschenden individuellen Begriffskonzepte zu beschreiben, fehlen insbesondere Studien in der Grundschule, die alle vier Klassenstufen betrachten und dabei differenzierte Erkenntnisse zu verschiedenen theoretischen Indikatoren des Begriffsverständnisses liefern. Daher geht die vorliegende Studie der Frage nach, welches Verständnis der Begriffe Viereck, Rechteck und Quadrat Schülerinnen und Schüler der Jahrgangsstufen 1, 2, 3 und 4 zeigen. Dazu wurde eine Quasi-Längsschnittstudie mit N = 456 Grundschulkindern (ca. 100 pro Jahrgangsstufe) durchgeführt. Die Ergebnisse geben detaillierte Einblicke in die individuellen Begriffskonzepte der Lernenden und zeigen, dass Lernende zunehmend Eigenschaften der Figuren berücksichtigen, jedoch individuelle Begriffskonzepte über lange Zeit auch prototypisch geprägt sind. Implikationen dieser Ergebnisse für Forschung und Praxis werden diskutiert.}}, author = {{Bruns, Julia and Unterhauser, Elisabeth and Gasteiger, Hedwig}}, issn = {{0173-5322}}, journal = {{Journal für Mathematik-Didaktik}}, keywords = {{Education, General Mathematics}}, number = {{2}}, pages = {{581--623}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Geometrisches Begriffsverständnis in der Grundschule am Beispiel der Begriffe Viereck, Rechteck und Quadrat}}}, doi = {{10.1007/s13138-021-00185-4}}, volume = {{42}}, year = {{2021}}, }