Allowed in a reference list, but should be avoided in Further Reading lists. Include [out of print] at the end of the reference citation. Date on which something went out of print is not necessary. For WSU Extension publications from 2005 or before, please mark them as out of print – they are in the process of being culled (a revision may be pending, but that won’t affect the status of the older version).

Example:

Antonelli, A. J., R.S. Byther, S.J. Collman, R. E. Thornton, and R. Van Denburgh. 2007. Home Gardens. Washington State University Extension Publication EB0422. Washington State University. [out of print].