let p, q be Element of CQC-WFF ; :: thesis: (p '&' q) => (('not' ('not' p)) '&' q) in TAUT
A1: (p => ('not' ('not' p))) => (('not' (('not' ('not' p)) '&' q)) => ('not' (p '&' q))) in TAUT by CQC_THE1:80;
p => ('not' ('not' p)) in TAUT by LUKASI_1:27;
then ('not' (('not' ('not' p)) '&' q)) => ('not' (p '&' q)) in TAUT by A1, CQC_THE1:82;
hence (p '&' q) => (('not' ('not' p)) '&' q) in TAUT by LUKASI_1:35; :: thesis: verum