Visite www.nga.gov e as seguintes referências impressas para obter mais informações:
- Boskovits, Miklós and David Alan Brown with Robert Echols, Gretchen A. Hirschauer, Eleonora Luciano, Rosamond E. Mack, Joseph Manca and J. Russell Sale. Italian paintings of the fifteenth century. Washington, DC: National Gallery of Art, 2003.
- Brady, Fred. “Angel Gabriel Stirs a Fuss, Is It or Isn’t It a Bust?” Boston Herald, July 19, 1965, 1 and 15.
- de Grazia, Diane and Eric Garberson et al. Italian paintings of the seventeenth and eighteenth centuries. Washington, DC: National Gallery of Art, 1996.
- Hand, John Oliver and Martha Wolff. Early Netherlandish painting. Washington, DC: National Gallery of Art, 1986.
- “Information Service.” Post Office Department, Philatelic Release No. 51, Aug 1, 1965, 1.
- “Information Service.” Press Release: General Release No. 85, July 14, 1965, 1-2.
- “Information Service.” Post Office Department, Philatelic Release No. 72, Nov 2, 1965, 1-6.
- “Information Service.” General Release. No. 75, June 11, 1966.
- “Information Service.” Philatelic Release No. 55, July 17, 1966, 1.
- “Information Service.” Remarks by Frederick C. Belen. No. 85, Nov. 1, 1966, 1.
- “Information Service.” Philatelic Release No. 81, Sept. 25, 1971, 1-3.
- “Information Service.” Postal Bulletin, Sept. 7, 1978.
- “Information Service.” Postal Bulletin, Sept. 29, 1988.
- “Information Service.” Postal Bulletin, Oct. 19, 1989.
- Kloetzel, James E, ed. Scott Stamp Monthly. Sidney, OH: Scott Publishing Co, 2008.
- Korcz, William.“Why I Collect Christmas as a Topic.” Yule Log Vol. 3, No. 10, October 1971, 1.
- National Gallery of Art. Paintings and sculpture from the Mellon collection. Washington, DC: National Gallery of Art, 1949.
- National Gallery of Art. Paintings and sculpture from the Kress collection. Washington, DC: National Gallery of Art, 1959.
- National Gallery of Art. Sculpture: An illustrated catalogue. Washington, DC: National Gallery of Art, 1994.
- Shapley, Fern Rusk. Catalogue of the Italian Paintings. Washington, DC: National Gallery of Art, 1979.
- United States Postal Service Historian. “Christmas Holiday Stamps.” December 2008, 1-9.
- Wunderly, Kathleen. “How religion became traditional: The evolution of U.S. Christmas Stamps.” Scott Stamp Monthly, Vol. 20 No. 12, Dec 2002, 20-22.
Nota: Os boletins postais e os lançamentos filatélicos encontram-se disponíveis no Arquivo do Terceiro Diretor-Geral Adjunto dos Correios, situado no Museu Postal Nacional.