Critical point theory in global analysis and differential topology : an introduction

by Morse, Marston, Cairns, Stewart S.
Published 1969

Dimension theory

by Nagami, Keiô
Published 1970

The geometry of geodesics

by Busemann, Herbert
Published 1955

Geometry of manifolds

by Bishop, Richard L.
Published 1964

The four-color problem

by Ore, Øystein
Published 1967