Covalent immobilization of cholinesterases in polyacrylamide hydrogels Andrianov, A.K.; Chupov, V.V.; Valuev, L.I.; Plate, N.A. Doklady Akademii Nauk SSSR 318(5): 1250-1253 1991 0002-3264 https://eurekamag.com/research/007/166/007166336.php