3. Hodnett ED. Caregiver support for women during childbirth (Cochrane Review). In: The Cochrane Library, Issue 1, 1999.       Oxford:     Update Software.
4. Humenick SS and Bugen LA. Mastery: The key to childbirth satisfaction? A study. Birth 1981;8(2):84-89.
5. Humenick SS. Mastery: The key to childbirth satisfaction? A review. Birth 1981;8(2):79-83.
6. Jimenez S. Supportive pain management strategies. In Childbirth Education: Practice, Research, and Theory. FH Nichols and SS Humenick, eds. Philadelphia: Saunders, 1988.
7. Klaus M et al. Maternal assistance and support in labor: father, nurse, midwife, or doula? Clin Consult Obstet Gynecol 1992;4(4):211-217.
8. Lieberman AB. Easing Labor Pain. Boston: Harvard Common Press, 1992.
9. Perez P. The Nurturing Touch at Birth. Katy, TX: Cutting Edge Press, 1997.
10. Simkin P. Just another day in a woman”s life? Women”s long-term perceptions of their first birth experience. Part I. Birth 1991;18(4):203-210.
11. Simkin P. Simkin”s Ratings of Comfort Measures for Childbirth. Waco, TX: Childbirth Graphics, 1997.
12. Simkin P. The Birth Partner. Boston: Harvard Common Press, 1989.
13. Simkin P, Whalley J, and Keppler A. Pregnancy, Childbirth, and the Newborn. Deephaven, MN: Meadowbrook Press, 1991.