ANH, Phạm Kỳ.
 Về bài toán tuần hoàn có chứa tham số bé.
<strong>VNU Journal of Science: Natural Sciences and Technology</strong>, [S.l.], v. 1, n. 2, june 1986.
ISSN 2588-1140.
Available at: &lt;<a href="https://js.vnu.edu.vn/NST/article/view/4043" target="_new">https://js.vnu.edu.vn/NST/article/view/4043</a>&gt;. Date accessed: 24 nov. 2024.