@MISC{QC_LANG2.MIZ,
  AUTHOR = {Bancerek, Grzegorz},
  TITLE = {Connectives and Subformulae of the First Order Language},
  DAY = {23},
  MONTH = {November},
  YEAR = {1989},
  ADDRESS1 = {Warsaw University\\Bia{\l}ystok},
  SUMMARY = {In the article the development of the first order language defined in
 \cite{QC_LANG1.ABS} is continued.
The following connectives are introduced: implication ($\Rightarrow$),
disjunction ($\vee$), and equivalence ($\Leftrightarrow$).
We introduce also the existential quantifier ($\exists$) and FALSUM.
Some theorems on disjunctive, conditional,
biconditional and existential formulae are proved and their selector functors
are introduced. The second part of the article deals with notions of
subformula, proper subformula and immediate constituent of a QC-formula.}}

