Structure of a group related to a Napoleon tessellation

Vlastimil Dlab started his mathematical career 1956 in algebra at the Charles University in Prague. Then, he had positions at the University of Khartoum, at the Institute of Advanced Studies in Canberra, Australia, and finally at Carleton University in Ottawa, Canada. He visited mathematics departments all around the world and was elected Fellow of the Royal Society of Canada in 1977. Presently he is Professor Emeritus and Distinguished Research Professor at Carleton University and Professor Hospitus at Charles University.