@book{401378, title = {Z\'aklady teorie grupoid\r u a grup}, series = {GDML\_Books}, publisher = {Nakladatelstv\'\i\ \v ceskoslovensk\'e akademie v\v ed}, address = {Praha}, year = {1962}, mrnumber = {MR0155921}, language = {cs}, url = {http://dml.mathdoc.fr/item/401378} }
Borůvka, Otakar. Základy teorie grupoidů a grup. GDML_Books (1962), http://gdmltest.u-ga.fr/item/401378/