Enhancement of standardized precipitation evapotranspiration index predictions by machine learning based on regression and soft computing for Iran’s arid and hyper–arid region - Saeid Bour; Zahra Kayhomayoon; Farhad Hassani; Sami Ghordoyee Milan; Ommolbanin Bazrafshan; Ronny Berndtsson (PLoS ONE, 2025)