begin
theorem Th1:
theorem Th2:
theorem Th3:
theorem Th4:
theorem
canceled;
theorem Th6:
theorem Th7:
theorem Th8:
theorem Th9:
theorem Th10:
theorem
theorem
theorem
canceled;
theorem
canceled;
theorem Th15:
theorem Th16:
theorem Th17:
theorem Th18:
theorem