Erkama, T. (1973). Group actions and extension problems for maps of balls. Suomalainen Tiedeakatemia.
Dyfyniad Arddull ChicagoErkama, Timo. Group Actions and Extension Problems for Maps of Balls. Helsinki: Suomalainen Tiedeakatemia, 1973.
Dyfyniad MLAErkama, Timo. Group Actions and Extension Problems for Maps of Balls. Suomalainen Tiedeakatemia, 1973.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.