Library of Congress (Washington), & Vollbehr, O. H. F. (1930). Exhibit of books printed during the XVth century and known as incunabula: List of books ; selected from the Vollbehr collection purchased by an act of Congress 1930. Washington: U.S. Gov. Print. Off.

Library of Congress (Washington), und Otto H. F. Vollbehr. Exhibit of Books Printed During the XVth Century and Known As Incunabula: List of Books ; Selected From the Vollbehr Collection Purchased By an Act of Congress 1930. Washington: U.S. Gov. Print. Off, 1930.

Library of Congress (Washington), und Otto H. F. Vollbehr. Exhibit of Books Printed During the XVth Century and Known As Incunabula: List of Books ; Selected From the Vollbehr Collection Purchased By an Act of Congress 1930. Washington: U.S. Gov. Print. Off, 1930.