{"author":[{"first_name":"Yulai","last_name":"Ma","full_name":"Ma, Yulai"},{"full_name":"Mattiolo, Davide","last_name":"Mattiolo","first_name":"Davide"},{"id":"15548","orcid":"0000-0002-9808-7401","full_name":"Steffen, Eckhard","last_name":"Steffen","first_name":"Eckhard"},{"full_name":"Wolf, Isaak H.","last_name":"Wolf","first_name":"Isaak H."}],"intvolume":"        45","status":"public","date_created":"2025-03-27T09:46:34Z","abstract":[{"lang":"eng","text":"An r-regular graph is an r-graph, if every odd set of vertices is connected to its complement by at least r edges. Let G and H be r-graphs. An H-coloring of G is a mapping such that each r adjacent edges of G are mapped to r adjacent edges of H. For every , let be an inclusion-wise minimal set of connected r-graphs, such that for every connected r-graph G there is an which colors G. The Petersen Coloring Conjecture states that consists of the Petersen graph P. We show that if true, then this is a very exclusive situation. Our main result is that either or is an infinite set and if , then is an infinite set. In particular, for all , is unique. We first characterize and then prove that if contains more than one element, then it is an infinite set. To obtain our main result we show that contains the smallest r-graphs of class 2 and the smallest poorly matchable r-graphs, and we determine the smallest r-graphs of class 2."}],"publication_identifier":{"issn":["0209-9683","1439-6912"]},"publisher":"Springer Science and Business Media LLC","date_updated":"2025-03-27T09:48:48Z","_id":"59169","type":"journal_article","issue":"2","citation":{"ieee":"Y. Ma, D. Mattiolo, E. Steffen, and I. H. Wolf, “Sets of r-Graphs that Color All r-Graphs,” <i>Combinatorica</i>, vol. 45, no. 2, Art. no. 16, 2025, doi: <a href=\"https://doi.org/10.1007/s00493-025-00144-4\">10.1007/s00493-025-00144-4</a>.","ama":"Ma Y, Mattiolo D, Steffen E, Wolf IH. Sets of r-Graphs that Color All r-Graphs. <i>Combinatorica</i>. 2025;45(2). doi:<a href=\"https://doi.org/10.1007/s00493-025-00144-4\">10.1007/s00493-025-00144-4</a>","mla":"Ma, Yulai, et al. “Sets of R-Graphs That Color All r-Graphs.” <i>Combinatorica</i>, vol. 45, no. 2, 16, Springer Science and Business Media LLC, 2025, doi:<a href=\"https://doi.org/10.1007/s00493-025-00144-4\">10.1007/s00493-025-00144-4</a>.","short":"Y. Ma, D. Mattiolo, E. Steffen, I.H. Wolf, Combinatorica 45 (2025).","bibtex":"@article{Ma_Mattiolo_Steffen_Wolf_2025, title={Sets of r-Graphs that Color All r-Graphs}, volume={45}, DOI={<a href=\"https://doi.org/10.1007/s00493-025-00144-4\">10.1007/s00493-025-00144-4</a>}, number={216}, journal={Combinatorica}, publisher={Springer Science and Business Media LLC}, author={Ma, Yulai and Mattiolo, Davide and Steffen, Eckhard and Wolf, Isaak H.}, year={2025} }","chicago":"Ma, Yulai, Davide Mattiolo, Eckhard Steffen, and Isaak H. Wolf. “Sets of R-Graphs That Color All r-Graphs.” <i>Combinatorica</i> 45, no. 2 (2025). <a href=\"https://doi.org/10.1007/s00493-025-00144-4\">https://doi.org/10.1007/s00493-025-00144-4</a>.","apa":"Ma, Y., Mattiolo, D., Steffen, E., &#38; Wolf, I. H. (2025). Sets of r-Graphs that Color All r-Graphs. <i>Combinatorica</i>, <i>45</i>(2), Article 16. <a href=\"https://doi.org/10.1007/s00493-025-00144-4\">https://doi.org/10.1007/s00493-025-00144-4</a>"},"department":[{"_id":"542"}],"publication_status":"published","language":[{"iso":"eng"}],"user_id":"15540","article_number":"16","year":"2025","doi":"10.1007/s00493-025-00144-4","publication":"Combinatorica","title":"Sets of r-Graphs that Color All r-Graphs","volume":45}