Sahijwani, L. ., and N. Sukavanam. “Approximate Controllability for Systems of Fractional Nonlinear Differential Equations Involving Riemann-Liouville Derivatives”. An International Journal of Optimization and Control: Theories & Applications (IJOCTA), vol. 13, no. 1, Jan. 2023, pp. 59-67, doi:10.11121/ijocta.2023.1178.