Setyowisnu, Glagah, 		Muzdalifah, Lilik, AND 		Saputro, Isnu.
" ASYMPTOTIC STUDY OF NONLINEAR SPRING OSCILLATION WITH EXTERNAL FORCE USING THE MULTIPLE TIME SCALES METHOD" <em>Jurnal Ilmiah Matematika dan Pendidikan Matematika</em> [Online], Volume 17 Number 2 (7 January 2026)