2 citations to https://www.mathnet.ru/rus/lncs11

1. Stepan L. Kuznetsov, “Complexity of the Lambek calculus and its extensions”, Stud. Comput. Intell., 1081 (2023), 1–29      
2. S. Kuznetsov, “$L$-completeness of the Lambek calculus with the reversal operation allowing empty antecedents”, Lecture Notes in Comput. Sci., 8222 (2014), 268–278