The Russo-Bulgarian military convention of 1902.
[By] E.C. Helmreich and C.E. Black.

APA Citation

Helmreich, E. Christian., Black, C. E. (Cyril Edwin). (1937). The Russo-Bulgarian military convention of 1902. [Chicago?.

MLA Citation

Helmreich, Ernst Christian, and Cyril E. (Cyril Edwin) Black. The Russo-Bulgarian Military Convention of 1902. [Chicago?, 1937.

Warning: These citations may not always be complete (especially for serials).