This paper presents a survey of formal models used as aids in solving practical NSP management problems at different levels. The models surveyed may be conveniently classified into two groups. The first deals with population, the second describes settlement systems and solves allocation problems. The list of models presented is not exhaustive but illustrates the main principles of model design. Thus the models do not necessarily belong to a single bibliographical source, but may be combinations of similar ideas represented by different sources. To identify the source, only basic references are given.