If you use GPTIPS (modified or not) in any published work then please include the following citations.
I didn't get paid to write GPTIPS, I work in a semi-academic environment and citations are important for my career.
If you like you can also buy me a coffee!
Searson D.P., In: Gandomi A., Alavi A., Ryan C. (eds) Handbook of Genetic Programming Applications. Springer, Cham. https://doi.org/10.1007/978-3-319-20883-1_22, 2015.
Available here: https://link.springer.com/chapter/10.1007/978-3-319-20883-1_22
No paywall author pre-print: https://arxiv.org/pdf/1412.4690
Searson, D.P., Leahy, D.E. & Willis, M.J.
Proceedings of the International MultiConference of Engineers and Computer Scientists 2010 (IMECS 2010), Hong Kong, 17-19 March, 2010.
This is freely available at: http://www.iaeng.org/publication/IMECS2010/IMECS2010_pp77-80pdf
Related papers that may be of interest.
These use multiple tree and multiple gene representations to generate statistical learning models (gradient boosted symbolic regression) and process control algorithms (symbolic reinforcement learning).
Dominic Searson, Mark Willis & Gary Montague
Journal of Chemometrics, 21(12), pp. 592 - 603, DOI: 10.1002/cem.1084, John Wiley and Sons, Ltd., 2007.
Available here: http://dx.doi.org/10.1002/cem.1084
Dominic Searson , Mark Willis , Gary Montague
in Hamza, M.H. (Ed.), Eighteenth IASTED International Conference on Modelling, Identification and Control, ACTA press, 1999.
Available here (no paywall) : https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.152.9591&rep=rep1&type=pdf