Astrauskienė, E., Liutauras Ragulskis, and Irena Tiknevičienė. “ On the Application of Two Small Parameters Method”. Lietuvos matematikos rinkinys 37, no. I (December 15, 1997): 236–240 . Accessed August 29, 2026. https://zurnalai.vu.lt/LMR/article/view/38227.