Distributed optimal control of a tumor growth treatment model with cross-diffusion effect P. T. Sowndarrajan, J. Manimaran, Amar Debbouche and L. Shangerganesh Eur. Phys. J. Plus, 134 9 (2019) 463 Published online: 25 September 2019 DOI: 10.1140/epjp/i2019-12866-8