reserve A,B,C for Ordinal,
  K,L,M,N for Cardinal,
  x,y,y1,y2,z,u for object,X,Y,Z,Z1,Z2 for set,
  n for Nat,
  f,f1,g,h for Function,
  Q,R for Relation;
reserve ff for Cardinal-Function;
reserve F,G for Cardinal-Function;

theorem Th43:
  card A in card B implies A in B
proof
  assume that
A1: card A in card B and
A2: not A in B;
  not card B c= card A by A1,CARD_1:4;
  hence contradiction by A2,CARD_1:11,ORDINAL1:16;
end;
