LYRENÄS , S.; NYBERG , F.; WILLDECK-LUND , G.; LINDSTRÖM , L.; LINDBERG , B.; TERENIUS , L. Endorphin Activity in Cerebrospinal Fluid Prior to Elective Cesarean Section and in Early Puerperium. Upsala Journal of Medical Sciences, v. 92, n. 1, p. 37-45, 1 Mar. 1987.