THI, Chau Ma; 						THANH, Long Vu; 						MINH, Kien Nguyen.
 Multi-Layer Virtual Keyboard Interface Based on Character Frequency for Vietnamese BCI Speller System.
<strong>VNU Journal of Science: Computer Science and Communication Engineering</strong>, [S.l.], v. 41, n. 2, dec. 2025.
ISSN 2588-1086.
Available at: &lt;<a href="//jcsce.vnu.edu.vn/index.php/jcsce/article/view/4084" target="_new">//jcsce.vnu.edu.vn/index.php/jcsce/article/view/4084</a>&gt;. Date accessed: 19 dec. 2025.
doi: <a href="https://doi.org/10.25073/2588-1086/vnucsce.4084">https://doi.org/10.25073/2588-1086/vnucsce.4084</a>.