@MISC{ORDERS_1.MIZ,
  AUTHOR = {Trybulec, Wojciech A.},
  TITLE = {Partially Ordered Sets},
  DAY = {30},
  MONTH = {August},
  YEAR = {1989},
  ADDRESS1 = {Warsaw University},
  SUMMARY = {   In the beginning of this article we define the choice function of
a non-empty set family that does not contain $\emptyset$ as introduced in
 \cite[pages 88--89]{KURAT:1}.
    We define order of a
set as a relation being reflexive, antisymmetric and transitive in the set,
 partially ordered set as structure non-empty set and order of the set,
chains, lower and upper cone of a subset, initial segments of element and
subset of partially ordered set.
  Some theorems that belong rather to \cite{ZFMISC_1.ABS}
 or \cite{RELAT_2.ABS} are proved.}}

