@MISC{SUBSET_1.MIZ,
  AUTHOR = {Trybulec, Zinaida},
  TITLE = {Properties of Subsets},
  DAY = {04},
  MONTH = {March},
  YEAR = {1989},
  ADDRESS1 = {Warsaw University\\Bia{\l}ystok},
  SUMMARY = {     The text includes theorems concerning properties
  of subsets, and some operations on sets.
  The functions yielding improper subsets of a set,
  i.e. the empty set and the set itself are introduced.
  Functions and predicates introduced for sets are
  redefined.
  Some theorems about enumerated sets are proved.}}

