1 06B23 1 15A30 1 15B33 1 16D90 1 16E10 1 16E35 1 16G10 1 16G20 1 16G30 1 16N60 1 16P40 1 16S90 1 16W22 1 18G20 1 2-monomial matrix 1 20D10 1 20D15 1 20D20 1 Amitsur property 1 Jacobson radical 1 Klein surfaces 1 Noetherian diagonal 1 \(\cal F\) -critical group,\(\cal F\) -maximal subgroup 1 \(\cal F\)-hypercentre 1 boundary condition 1 closed submodule 1 closure operator 1 commutative ring 1 dense submodule 1