Optical and acoustic polaron formation: Dynamic matrix approach (DMA) M. N. Jipdi, I. F. Fokou, M. Tchoffo and L. C. Fai Eur. Phys. J. Plus, 134 10 (2019) 525 Published online: 23 October 2019 DOI: 10.1140/epjp/i2019-12902-9