Higher de Rham-Witt complexes of supersingular K3 surfaces Niels O. Nygaard — 1980 Compositio Mathematica
Construction of some classes in the cohomology of Siegel modular threefolds Niels O. Nygaard — 1995 Compositio Mathematica
Slopes of powers of Frobenius on crystalline cohomology Niels O. Nygaard — 1981 Annales scientifiques de l'École Normale Supérieure
Closedness of regular 1 -forms on algebraic surfaces Niels O. Nygaard — 1979 Annales scientifiques de l'École Normale Supérieure
A Short Proof of the Rydakov-Safarevic Theorem. William E. Lang; Niels O. Nygaard — 1980 Mathematische Annalen