Removal of instabilities of the higher derivative theories in the light of antilinearity Biswajit Paul, Himangshu Dhar and Biswajit Saha Eur. Phys. J. C, 81 8 (2021) 770 Published online: 26 August 2021 DOI: 10.1140/epjc/s10052-021-09553-3