let p, q be Element of CQC-WFF ; :: thesis: ('not' (p 'or' q)) => (('not' p) '&' ('not' q)) in TAUT
'not' (p 'or' q) = 'not' ('not' (('not' p) '&' ('not' q))) by QC_LANG2:def 3;
hence ('not' (p 'or' q)) => (('not' p) '&' ('not' q)) in TAUT by LUKASI_1:25; :: thesis: verum