Grove, E. A., E. Lapierre, and W. Tikjha. “On the Global Behavior of 𝑥ᵤ₊₁ = |𝑥ᵤ|− 𝑦ᵤ − 1 and 𝑦ᵤ₊₁ = 𝑥ᵤ +|𝑦ᵤ|”. CUBO, A Mathematical Journal, vol. 14, no. 2, June 2012, pp. 111–152, doi:10.4067/S0719-06462012000200007.