theorem Th101:
  |-_IPC FALSUM 'equiv' (p '&' (p => FALSUM))
proof
A1: |-_IPC FALSUM => (p '&' (p => FALSUM)) by Th36;
  |-_IPC (p '&' (p => FALSUM)) => FALSUM by Th100;
  hence thesis by A1,Th84;
end;
