Katzaroff's patent directory.
Katsarov, Konstantin.
Sofia : K. Katzaroff,
Vol. for 1931 includes the supplement: Patents, trade marks, models and designs in East Europe.
Title varies slightly.
Description based on: 1940.
Vol. for 1931 includes the supplement: Patents, trade marks, models and designs in East Europe.
Patents (International law)
Manual and directory on industrial property all over the world