http://erepo.unud.ac.id/id/eprint/18819/1/84f792be708bd93a0e18dde1c592ca79.pdf
https://www.ncbi.nlm.nih.gov/books/NBK470399/
https://www.scribd.com/embeds/517260338/content?start_page=1&view_mode=scroll&access_key=key-fFexxf7r1bzEfWu3HKwf
