1. Anderson, M., Feil, T.: Lattice-Ordered Groups: an Introduction. Reidel Texts in the Mathematical Sciences. D. Reidel Publishing Company (1988)
2. Chitayat, M., Daigle, D.: On the rigidity of certain Pham-Brieskorn rings. J. Algebra 550, 290–308 (2020)
3. Daigle, D.: Introduction to locally nilpotent derivations. Informal lecture notes prepared in 2010, available at http://aix1.uottawa.ca/~ddaigle
4. Daigle, D.: Tame and wild degree functions. Osaka J. Math. 49, 53–80 (2012)
5. Daigle, D., Freudenburg, G., Moser-Jauslin, L.: Locally nilpotent derivations of rings graded by an abelian group. In: Algebraic Varieties and Automorphism Groups, vol. 75 of Adv. Stud. Pure Math., pp. 29–48. Math. Soc. Japan, Tokyo (2017)