Grove, E. A.; Lapierre, E.; Tikjha, W. On the Global Behavior of 𝑥ᵤ₊₁ = |𝑥ᵤ|− 𝑦ᵤ − 1 and 𝑦ᵤ₊₁ = 𝑥ᵤ +|𝑦ᵤ|. CUBO 2012, 14, 111–152.