https://uomosul.edu.iq/dentistry/%d9%88%d8%b1%d8%b4%d8%a9-%d8%b9%d9%85%d9%84-%d8%a8%d8%b9%d9%86%d9%88%d8%a7%d9%86-uses-of-spectrophoyometer-in-dentistr/