A New Proof for Folner's Condition for Maximally Almost Periodic Groups. Per Tomter — 1966 Mathematica Scandinavica
On minimal immersions of S n - 1 into S n ( 1 ) , n ≥ 4 Wu-yi Hsiang; Per Tomter — 1987 Annales scientifiques de l'École Normale Supérieure
On the existence of minimal hyperspheres in compact symmetric spaces Wu-teh Hsiang; Wu-yi Hsiang; Per Tomter — 1988 Annales scientifiques de l'École Normale Supérieure