Abs, R. Catalogue: Lettres, documents, manuscrits, etc. Bruxelles: Institut Emile Vandervelde.
Cita Chicago (17th ed.)Abs, Robert. Catalogue: Lettres, Documents, Manuscrits, Etc. Bruxelles: Institut Emile Vandervelde.
Cita MLA (8th ed.)Abs, Robert. Catalogue: Lettres, Documents, Manuscrits, Etc. Bruxelles: Institut Emile Vandervelde.
Atenció: Aquestes cites poden no estar 100% correctes.