Sindbad~EG File Manager

PGABCD
PGEFGH
COADE
COADH
COBCF
COBCG
EEBCFG
ANPRABCD+PRADBC  defn:parallelogram
ANPREFGH+PREHFG  defn:parallelogram
PRABCD
PREFGH
PREHFG
NCEHG  lemma:parallelNC
NEEH   lemma:NCdistinct
NCABC  lemma:parallelNC
NEBC  lemma:NCdistinct
EEEHFG   proposition:34
EEFGEH   lemma:congruencesymmetric
EEBCEH   lemma:congruencetransitive
PRADBC   
PRBCAD  lemma:parallelsymmetric
PRBCEH   lemma:collinearparallel2
PREHBC  lemma:parallelsymmetric
EEEHBC  lemma:congruencesymmetric
NOORCRECBH|CREBHC assumption
 ANNOCRECBH+NOCREBHC
 NOCRECBH
 NOCREBHC
 CRECBH  lemma:crisscross
ORCRECBH|CREBHC reductio
cases EFABCDEFGH:CRECBH|CREBHC
 case 1:CRECBH
  ANBEEMC+BEBMH  defn:cross
  BEEMC
  BEBMH
  BEHMB  axiom:betweennesssymmetry
  ANPREBHC+EEEBHC  proposition:33
  PREBHC
  PREBCH  lemma:parallelflip
  PGEBCH defn:parallelogram
  EFABCDEBCH  proposition:35
  COBCF
  COBCG
  NEBC
  COCFG  lemma:collinear4
  COGFC  lemma:collinearorder
  COCBF  lemma:collinearorder
  COCBG  lemma:collinearorder
  NECB   lemma:inequalitysymmetric
  COBFG  lemma:collinear4
  COGFB  lemma:collinearorder
  PREHFG
  PRFGEH  lemma:parallelsymmetric
  PRGFHE  lemma:parallelflip
  PREFGH  defn:parallelogram
  PRGHEF   lemma:parallelsymmetric 
  ANPRGHEF+PRGFHE
  PGGHEF  defn:parallelogram
  PREBCH
  PRCHEB lemma:parallelsymmetric
  PREHBC
  PRBCEH lemma:parallelsymmetric
  PRCBHE lemma:parallelflip
  ANPRCHEB+PRCBHE
  PGCHEB  defn:parallelogram
  EFGHEFCHEB  proposition:35
  EFGHEFEBCH axiom:EFpermutation
  EFEBCHGHEF axiom:EFsymmetric
  EFABCDGHEF axiom:EFtransitive
  EFABCDEFGH axiom:EFpermutation
 qedcase
 case 2:CREBHC 
  ANBEEMB+BEHMC  defn:cross
  BEEMB
  BEHMC
  PRHEBC  lemma:parallelflip
  EEHEBC  lemma:congruenceflip
  ANPRHBEC+EEHBEC  proposition:33
  PRHBEC
  PRHBCE  lemma:parallelflip
  PGHBCE defn:parallelogram
  EFABCDHBCE  proposition:35
  COBCF
  COBCG
  NEBC
  COCGF  lemma:collinear4
  COFGC  lemma:collinearorder
  COCBG  lemma:collinearorder
  COCBF  lemma:collinearorder
  NECB   lemma:inequalitysymmetric
  COBGF  lemma:collinear4
  COFGB  lemma:collinearorder
  PRHEFG  lemma:parallelflip
  PRFGHE  lemma:parallelsymmetric
  PRFGEH  lemma:parallelflip
  PRFEHG  lemma:parallelflip
  ANPRFEHG+PRFGEH
  PGFEHG  defn:parallelogram
  PRHBCE
  PRCEHB lemma:parallelsymmetric
  PRCBEH lemma:parallelflip
  ANPRCEHB+PRCBEH
  PGCEHB  defn:parallelogram
  EFFEHGCEHB  proposition:35
  EFFEHGHBCE axiom:EFpermutation
  EFHBCEFEHG axiom:EFsymmetric
  EFABCDFEHG axiom:EFtransitive
  EFABCDEFGH axiom:EFpermutation
 qedcase
EFABCDEFGH cases