Kumpel, P. G. (1975), „Do similar figures always have the same shape?”, The Mathematics Teacher, 68 (8): 626—628, ISSN0025-5769, doi:10.5951/MT.68.8.0626.
Kumpel, P. G. (1975), „Do similar figures always have the same shape?”, The Mathematics Teacher, 68 (8): 626—628, ISSN0025-5769, doi:10.5951/MT.68.8.0626.