Dr. Jan Oskar de Gruyter.

MLA

De Bom, Emmanuel. Dr. Jan Oskar De Gruyter. s.l, 1930.

APA

De Bom, E. (1930). Dr. Jan Oskar de Gruyter. s.l.

Chicago

De Bom, Emmanuel Dr. Jan Oskar De Gruyter. s.l., 1930.