The equivariant Dehn's lemma and loop theorem. Shing-Tung Yau, W.H. Meeks III (1981) Commentarii mathematici Helvetici
The incidence submanifold of R P n × G 1 ( R P n ) for n odd is nonorientable Eugen Ružický (1976) Mathematica Slovaca
The Three Big Theorems of Papakyriakopoulos V. Poenaru (1977) Δελτίο της Ελληνικής Μαθηματικής Εταιρίας