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. ujms 1987, 92, 37-45.