Bodies of Constant Width Horst Martini, Luis Montejano, Déborah Oliveros E-Book (pdf)

Circles, Spheres and Spherical Geometry Hiroshi Maehara, Horst Martini E-Book (pdf)

Convexity from the Geometric Point of View Vitor Balestro, Horst Martini, Ralph Teixeira E-Book (pdf)