theorem Th3:
  (p '&' q) => r is valid implies p => (q => r) is valid
proof
A1: ((p '&' q) => r) => (p => (q => r)) in TAUT(A) by PROCAL_1:31;
  assume (p '&' q) => r in TAUT(A);
  hence (p => (q => r)) in TAUT(A) by A1,CQC_THE1:46;
end;
