Dücker, M., Geiger, C., Lehrenfeld, G., Müller, W., &; Tahedl, C. (1997). A Visual Programming Language for Qualitative Data. Proceedings of the 1997 IEEE Symposium on Visual Languages.https://doi.org/10.1109/VL.1997.626593 
LibreCat: /record/39510
DOI: 10.1109/VL.1997.626593