Mohamed م. إ. س., “SUBJECT INDEX (Volume 21 – 2017): Subject index of research papers published in the ‘University of Aden Journal of Natural & Applied Sciences’, and their authors Volume 21 (April - December 2017)”, Univ. Aden J. Nat. and Appl. Sc., vol. 22, no. 1, pp. 75–80 & 223, Apr. 2018.