อ้างอิง

https://yuinongluk.wordpress.com/%E0%B8%AB%E0%B9%88%E0%B8%A7%E0%B8%87%E0%B9%82%E0%B8%8B%E0%B9%88%E0%B8%AD%E0%B8%B2%E0%B8%AB%E0%B8%B2%E0%B8%A3-food-chain/

http://kanchanapisek.or.th/kp6/sub/book/book.php?book=17&chap=3&page=t17-3-infodetail04.html