Funding for this research was provided by:
Vietnam Ministry of Education and Training (B2021-SPH-01.)
Received: 18 August 2021
Accepted: 7 September 2021
First Online: 17 November 2021
: Not applicable. The study does not involve human subjects, only used public data.
: Not applicable.
: The authors declare that there is no competing interest in relation to the publication of this article.