Clute, John. "Greg Bear." In The Encyclopedia of Science Fiction. Edited by John Clute, Peter Nicholls, et al. New York: St. Martin's/Griffin, 1995, pp. 99-100. An overview of Bear's career, emphasizing the relationship of his writings to the period in which they were written, mostly in the 1980s.

Heads 153 Easton, Tom. Review. Analog Science Fiction and Fact 112, 1-2 (January 1992): 310-11.

Easton is unimpressed by Heads.

Natke, Nora Jane. Review. School Library Journal 38, 4 (April 1992): 163. Natke expresses mild approval for Heads.

Perlberg, Marilyn A. "Greg Bear." Beacham's Encyclopedia of Popular Fiction. Edited by Kirk H. Beetz. Osprey, FL: Beacham Publishing, 1996, pp. 114-17. Perlberg summarizes Bear's life, career, and critical reception and provides a heavily annotated bibliography of resources for learning more about him.

Publishers Weekly 238, 32 (July 25, 1991): 4041. A not particularly informative but favorable review of Heads.