Laurence Stockton Helffrich poster stamp collection, 1918, Box: 1; Box: 2. Division of Rare and Manuscript Collections.
Laurence Stockton Helffrich poster stamp collection, 1918, Box: 1; Box: 2. Division of Rare and Manuscript Collections. https://archives.library.cornell.edu/repositories/2/resources/3442 Accessed January 19, 2026.
