theorem
  p is conjunctive implies ex q,r st p = q '&' r
proof
  assume p is conjunctive;
  then consider q, r being Element of QC-WFF(A) such that
A1: p = q '&' r by QC_LANG1:def 20;
A2: r is Element of CQC-WFF(A) by A1,CQC_LANG:9;
  q is Element of CQC-WFF(A) by A1,CQC_LANG:9;
  hence thesis by A1,A2;
end;
