- Series: Letters: Robert A. Heinlein Series Record # 66044
- Letters: Robert A. Heinlein
- Letter (Sweetness and Light, Spring 1940) (1940) [ES] by Robert A. Heinlein [only as by Bob Heinlein]
- Letter (Inside Information) (1947) [ES] by Robert A. Heinlein
- Letter (Astounding, November 1947) (1947) [ES] by Robert A. Heinlein [only as by Bob]
- Letter: Xenobiology (Science V124) (1961) [ES] by Robert A. Heinlein
- Letter (Harris Public Library Children's Literary Magazine) (1966) [ES] by Robert A. Heinlein
- Letter to the Officers and Members of LASFS (1974) [ES] by Robert A. Heinlein
- Letter (Survive Magazine) (1982) [ES] by Robert A. Heinlein
- Letter (Locus #268) (1983) [ES] by Robert A. Heinlein
- Letter (Locus #327) (1988) [ES] by Robert A. Heinlein
- Letter to Theodore Sturgeon, February 11, 1955 (1995) [ES] by Robert A. Heinlein [only as by Robert Heinlein]
- Letter to Jack Williamson, 29 April 1983 (2011) [ES] by Robert A. Heinlein
- Letter Appeal for Stanford Hospital (2011) [ES] by Robert A. Heinlein
- Letter: Tribute to Grand Master Jack Williamson (2011) [ES] by Robert A. Heinlein
- Letter-Article for Clifford Simak (2011) [ES] by Robert A. Heinlein
- Letter to T. B. Buell about Fleet Admiral Ernest King, 3 October 1974 (2011) [ES] by Robert A. Heinlein
- Letter to LASFS (via Jerry Pournelle) (2011) [ES] by Robert A. Heinlein
- Letter to Mr. James Doherty, 24 June 1959 (2012) [ES] by Robert A. Heinlein
- Letter to Messrs. Swicegood and Doherty, June 30, 1959 (2012) [ES] by Robert A. Heinlein