M. T. PHẠM, T. T. LÊ, and S. NGÔ, “Effects of plant growth regulators, mineral medium, and pH values on the callus induction of young stem cutting slices of Ehretia asperula Zoll. et Mor.”, Science & Technology Development Journal: Natural Sciences, vol. 4, no. 2, pp. 458-467, Jun. 2020.