G. Stumme. Ordinal and Symbolic Data Analysis. Proc. OSDA'95. Studies in Classification, Data Analysis, and Knowledge Organization 8, стр. 31-44. Heidelberg, Springer, (1996)
J. Hereth, G. Stumme, R. Wille, и U. Wille. Conceptual Structures: Logical, Linguistic, and Computational Issues. Proc. ICCS '00, том 1867 из LNAI, стр. 421-437. Heidelberg, Springer, (2000)