E. A. Grove, E. Lapierre, and W. Tikjha, “On the global behavior of 𝑥ᵤ₊₁ = |𝑥ᵤ|− 𝑦ᵤ − 1 and 𝑦ᵤ₊₁ = 𝑥ᵤ +|𝑦ᵤ|”, CUBO, vol. 14, no. 2, pp. 111–152, Jun. 2012.