Lyrenäs S., Nyberg F., Willdeck-Lund G., Lindström L., Lindberg B., & Terenius L. (1987). Endorphin Activity in Cerebrospinal Fluid Prior to Elective Cesarean Section and in Early Puerperium. Upsala Journal of Medical Sciences, 92(1), 37-45. https://doi.org/10.3109/03009738709178676