y ▁of ▁Set ▁Theory . ▁D over ▁repr int . ▁We ak ▁on ▁met at he ory ; ▁the ▁author ▁is ▁not ▁a ▁math ematic ian . ▁ ▁Tour lak is , ▁George , ▁ 2 0 0 3 . ▁L ect ures ▁in ▁Log ic ▁and ▁Set ▁Theory , ▁Vol . ▁ 2 . ▁Cambridge ▁University ▁Press . ▁ ▁Jean ▁van ▁He ij eno ort , ▁ 1 9 6 7 . ▁From ▁Fre ge ▁to ▁Gö del : ▁A ▁Source ▁Book ▁in ▁Mathemat ical ▁Log ic , ▁ 1 8 7 9 – 1 9 3 1 . ▁Harvard ▁University ▁Press . ▁In cludes ▁annot ated ▁English ▁transl ations ▁of ▁the ▁classic ▁articles ▁by ▁Z erm elo , ▁Fra enk el , ▁and ▁Sk ole m ▁bearing ▁on ▁Z FC . ▁ ▁. ▁▁ ▁English ▁translation ▁in ▁ ▁External ▁links ▁▁▁▁▁ ▁Stan ford ▁Encyclopedia ▁of ▁Philosoph y ▁articles ▁by ▁Thomas ▁Je ch : ▁ ▁Set ▁Theory ; ▁ ▁A xi oms ▁of ▁Z erm elo – F ra enk el ▁Set ▁Theory . ▁ ▁Met am ath ▁version ▁of ▁the ▁Z FC ▁ax i oms ▁— ▁A ▁conc ise ▁and ▁non redu nd ant ▁ax iom at ization . ▁The ▁background ▁first ▁order ▁logic ▁is ▁defined ▁especially ▁to ▁facil itate ▁machine ▁ver ification ▁of ▁proofs . ▁ ▁A ▁deriv ation ▁in ▁Met am ath ▁of ▁a ▁version ▁of ▁the ▁separation ▁schema ▁from ▁a ▁version ▁of ▁the ▁replacement ▁schema . ▁▁▁▁▁ ▁Category : System s ▁of ▁set ▁theory ▁Category : Z ▁notation