190 algebra algebraicstructures complementedlattices completenesstheorem computablefunctions equationalclasses functortheory generalalgebraicsystems grouptheory history homological kleenealgebra lattices latticetheory logic mathematicallogicandfoundations mathematics modern modularlattices music musicandscience musictheory order orderedalgebraicstructures philosophy philosophyandaesthetics semantics stochasticprocesses symbolicandmathematical universal universalalgebra varieties varieties(universalalgebra)