Hertzsprung-Kapteyn, Henrietta, b. 1881.
The life and works of J. C. Kapteyn / by Henrietta Hertzsprung-Kapteyn ; an annotated translation with preface and introduction by E. Robert Paul.
Kapteyn, J. C. (Jacobus Cornelius), 1851-1922
Astronomy -- Netherlands -- History.
Astronomers -- Netherlands -- Biography.
Paul, Erich Robert, 1943-