Items

• [E1902AK], Letter from Smithsonian Institution, Charles Greeley Abbot to Walter Halfin, October 11th, 1918
  1918-10-11
• [E1902AL], Letter from Scientific American to Walter Halfin, January 16th, 1919
  1919-01-16
• [E1902AM], Letter from Thomas Alva Edison to Walter Halfin, April 28th, 1919
  1919-04-28