Relativistic core-envelope anisotropic fluid model of super dense stars Satyanarayana Gedela, Neeraj Pant, Jaya Upreti and R. P. Pant Eur. Phys. J. C, 79 7 (2019) 566 Published online: 05 July 2019 DOI: 10.1140/epjc/s10052-019-7074-z