J. Agurto Zurita, N. Jarama Solarte, R. Allauca Arevalo, and C. Vaca Mendieta, “20 cases of fentanyl-associated ataranalgesia”, Revista UG, vol. 91, no. 3, pp. 51–62, Dec. 1994, doi: 10.53591/rug.v91i3.965.