Setting forth the problems Some history Synopsis of the main results Preliminaries The McPolin-Wickstead and Huijsmans-de Pagter-Koldunov Theorems revisited d-bases Band preserving operators and band-projections Central operators and Problems A and B Range-domain exchange in the Huijsmans-de Pagter-Koldunov Theorem d-splitting number of disjointness preserving operators Essentially one-dimensional and discrete vector lattices Essentially constant functions and operators on $C[0,1]$ Counterexamples Dedekind complete vector lattices and Problems A and B Generalizations to $(r_u)$-complete vector lattices Open problems References Index.