▁also ▁ ▁Error s - in - variables ▁model # Linear ▁model ▁ ▁Inst rument al ▁variable # Ident ification ▁ ▁Sim ult aneous ▁equations ▁model ▁ ▁System ▁of ▁linear ▁equations ▁ ▁References ▁▁▁▁▁▁▁▁▁▁▁▁ ▁(" A ▁classic ▁and ▁master ful ▁ex position ▁of ▁the ▁subject ", ▁, ▁p .   3 1 ) ▁ ▁External ▁links ▁▁ ▁by ▁Mark ▁Th oma ▁ ▁Category : Est imation ▁theory <0x0A> </s> ▁Br at ▁Tor , ▁also ▁known ▁as ▁Bra i ▁Tor ▁and ▁W id g ery ▁Tor , ▁is ▁a ▁dram atic ▁gran ite ▁tor ▁on ▁the ▁western ▁fl ank ▁of ▁D art mo or , ▁England . ▁It ▁is ▁best ▁known ▁for ▁W id g ery ▁Cross , ▁the ▁tall est ▁D art mo or ▁cross , ▁which ▁stands ▁on ▁its ▁sum mit . ▁It ▁is , ▁however , ▁not ▁as ▁grand ▁as ▁other ▁neighbour ing ▁t ors , ▁such ▁as ▁the ▁impos ing ▁Great ▁Link s ▁Tor ▁and ▁H are ▁Tor . ▁It ▁stands ▁at ▁ 4 5 4 ▁metres ▁above ▁sea ▁level . ▁ ▁References ▁ ▁Category : Ge ography ▁of ▁Dev on ▁Category : T ors ▁of ▁D art mo or ▁Category : D art mo or <0x0A> </s> ▁A ▁cart ogram ▁is ▁a ▁map ▁in ▁which ▁some ▁them atic ▁mapping ▁variable ▁– ▁such ▁as ▁travel ▁time , ▁population , ▁or ▁G NP ▁– ▁is ▁subst it uted ▁for ▁land ▁area ▁or ▁distance . ▁The ▁geometry ▁or ▁space ▁of ▁the ▁map ▁is ▁dist orted , ▁sometimes ▁extremely , ▁in ▁order ▁to