https://docs.google.com/document/d/1gHmMbxxD8RWvtsgYGAfs8CTS7xAmNnd8J4M3rEKfG1U/edit?usp=sharing

I personally used

https://www.theeastafrican.co.ke/business/Minerals-in-your-mobile-phone-/2560-2739730-jj0785/index.html