let p, q, r be Element of CQC-WFF ; :: thesis: (p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) is valid
(p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) in TAUT by Def1, Th76;
hence (p => q) => (('not' (q '&' r)) => ('not' (p '&' r))) is valid by Lm13; :: thesis: verum