Putra, Achmad Ferdiansyah Pradana, et al. “Characterization of Hydroxyapatite From Kupang Shells and Its Synthesis With Polycaprolactone for 3D Printing Filament”. IPTEK The Journal of Engineering, vol. 9, no. 2, Sept. 2025, pp. 47-51, https://journal.its.ac.id/index.php/joe/article/view/8179.