1
Pioneer of Galactic Astronomy : A Biography of Jacobus C. Kapteyn [E-Book] /
2
Master of Galactic Astronomy : A Biography of Jan Hendrik Oort [E-Book] /
3
Jan Hendrik Oort [E-Book] : Master of the Galactic System /
Other Personal Name(s): ...van der Kruit, Pieter C....

Full text 
4
Jacobus Cornelius Kapteyn [E-Book] : Born Investigator of the Heavens /