A sharp four dimensional isoperimetric inequality. Christopher B. Croke — 1984 Commentarii mathematici Helvetici
Rigidity for surfaces of non-positive curvature. Christopher B. Croke — 1990 Commentarii mathematici Helvetici
Some isoperimetric inequalities and eigenvalue estimates Christopher B. Croke — 1980 Annales scientifiques de l'École Normale Supérieure
On tori without conjugate points. Christopher B. Croke; Bruce Kleiner — 1995 Inventiones mathematicae