scientific article published in February 1969

Published in "Colloquia Mathematica Societatis Janos Bolyai"

scientific article published in 1971

scientific article published in 1977

scientific article published in 1957

doctoral dissertation by Mary Ellen Estill Rudin

scientific article published in 1992

scientific article published in June 1977

scientific article published in 1992

scientific article published in 2001

scientific paper

scientific article published in 1969

scientific article published in October 1976