Heppner, P. P., Wampold, B. E., & Kivlighan, D. M. (1999). Research design in counseling (2nd ed.). Brooks/Cole/Wadsworth.
Lua i Stíl Chicago (17ú heag.)Heppner, P. Paul, Bruce E. Wampold, agus Dennis M. Kivlighan. Research Design in Counseling. 2nd ed. Belmont, CA: Brooks/Cole/Wadsworth, 1999.
Lua MLA (9ú heag.)Heppner, P. Paul, et al. Research Design in Counseling. 2nd ed. Brooks/Cole/Wadsworth, 1999.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.