  The main objective of this paper is to investigate the explicit form,
stability character and global behavior of solutions of the following two
systems of rational difference equations
  x_{n+1}=((+(-)1)/(y_{n}(x_{n-1}+(-)1)+1)),
y_{n+1}=((+(-)1)/(x_{n}(y_{n-1}+(-)1)+1)), n=0,1,...
  such that their solutions are associated with Tribonacci numbers.
