Natural Dyes as pH indicator: a review. مجلة اليرموك, [S. l.], v. 21, n. 2, p. 22–29, 2023. Disponível em: https://journal.al-yarmok.edu.iq/index.php/alyarmoukjournal/article/view/97. Acesso em: 28 مارس. 2026.