Robson, B. A.2026-01-022026-01-020375-9474ORCID:/0000-0001-7845-9661/work/190592533https://hdl.handle.net/1885/733802327The Bloch L-operator is derived by the rigorous formal method of Mikusinski from simple assumptions concerning the expansion of wave functions and their derivatives in terms of a complete set of orthonormal continuous functions and their derivatives defined within an internal region.4en© 1969 The Author(s)1969-07-1410.1016/0375-9474(69)90608-30041707820