Nelken, H. (1980). Alexander von Humboldt: His portraits and their artists; a documentary iconography. Reimer.
Chicago Style (17th ed.) CitationNelken, Halina. Alexander Von Humboldt: His Portraits and Their Artists; a Documentary Iconography. Berlin: Reimer, 1980.
MLA (8th ed.) CitationNelken, Halina. Alexander Von Humboldt: His Portraits and Their Artists; a Documentary Iconography. Reimer, 1980.
Warning: These citations may not always be 100% accurate.