Ilmi, F., and Sulistiyawati. “Morphology and Anatomy of Species Heterocentrotus Trigonarius and Tripneustes Ventricosus (Echinodermata: Echinoidea) in Nguyahan Beach Gunungkidul”. Proceeding International Conference on Science and Engineering, vol. 4, Feb. 2021, pp. 129-32, http://sunankalijaga.org/prosiding/index.php/icse/article/view/643.