RT Journal T1 ON A COUPLED INTEGRO-DIFFERENTIAL SYSTEM INVOLVING MIXED FRACTIONAL DERIVATIVES AND INTEGRALS OF DIFFERENT ORDERS A1 Bashir AHMAD, Ravi P. AGARWAL, Abrar BROOM, Ahmed ALSAEDI PB Acta mathematica scientia,Series B FD 2021-08-25 YR 2021 JF Acta mathematica scientia, Series B JO Acta mathematica scientia,Series B VO 41 IS 4 SP 1366 DO 10.1007/s10473-021-0420-x K1 Fractional differential equations;Caputo and Riemann-Liouville fractional derivatives;systems;existence;fixed point theorems LK {http://121.43.60.238/sxwlxbB/EN/article/article_16483.shtml}