Weakly nonlinear analyses on double-diffusive convection of Casson fluid in a porous medium with an internal heat and gravity modulationL. Venkat Reddy, Ravi Ragoju, Suman Shekhar and Dhananjay YadavEur. Phys. J. B, 98 5 (2025) 97DOI: https://doi.org/10.1140/epjb/s10051-025-00947-w