The Rise and Fall of the Space Shuttle, Book Review: FINAL COUNTDOWN: NASA and the End of the Space Shuttle Program by Pat Duggins, American Scientist, 2008, Vol. 96, No. 5, p. 32.
computer-dictionary-online.org
„Hal/S”. Computer Dictionary Online. Arhivirano iz originala na datum 2007-10-18. Pristupljeno 2011-07-23.