reserve L for satisfying_Sh_1 non empty ShefferStr;
reserve L for satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3
  non empty ShefferStr;
reserve v,q,p,w,z,y,x for Element of L;

theorem Th161:
  L is satisfying_Sh_1
proof
  given a, b, c being Element of L such that
A1: (a | ((b | a) | a)) | (b | (c | a)) <> b;
A2: a | ((b | a) | a) = b | a by Th126;
  not ((a | ((b | a) | a)) | (b | (a | c))) = b by A1,Th83;
  hence thesis by A2,Th160;
end;
