Worku, A. . “A CLOSED-FORM SOLUTION PROCEDURE TO THE VIBRA TlON OF NON-CLASSICALLY DAMPED SYSTEMS SUBJECTED TO HARMONIC LOADS”. Zede Journal of Ethiopian Engineers and Architects, vol. 22, Jan. 2023, pp. 1-9, http://ejol.aau.edu.et/index.php/ZEDE/article/view/6515.