This paper treats, from an user point of view, the structure of the entities in the information base (IB) of a System for information servicing of collectivities (SISC) as well as the operations on these entries.
Barnev, P., Radensky, A. Structure of the Information Base and Operations on the Entities in a System for Information Servicing of Collectivitie Serdica, Bulgaricae Mathematicae Publicationes, Vol. 4, No, 2-3, 1978, Bulgarian Academy of Sciences Press, 180-183. http://www.math.bas.bg/serdica/1978.html
Bulgarian Academy of Sciences