Webber, B., & Webber, M. (1991). Index to Postmarked Washington: An encyclopedia of postal history combining the counties of Asotin, Spokane, Whitman, and all names mentioned in the section on Railway post offices in Washington State, (volume 1) 1858-1987. Webb Research Group.
Style de citation Chicago (17e éd.)Webber, Bert, et Margie Webber. Index to Postmarked Washington: An Encyclopedia of Postal History Combining the Counties of Asotin, Spokane, Whitman, and All Names Mentioned in the Section on Railway Post Offices in Washington State, (volume 1) 1858-1987. Medford, OR: Webb Research Group, 1991.
Style de citation MLA (8e éd.)Webber, Bert, et Margie Webber. Index to Postmarked Washington: An Encyclopedia of Postal History Combining the Counties of Asotin, Spokane, Whitman, and All Names Mentioned in the Section on Railway Post Offices in Washington State, (volume 1) 1858-1987. Webb Research Group, 1991.