If you ever had a hard time drawing anything, especially manga, these special references of specifically their eyes have been greatly made by an artist who wishes to help others. He’s created these of the animes Naruto, Bleach, Fairy Tail, as well as others such as Avatar, Full Metal Alchemist and Soul Eater which are not shown here.
If you wish to view the references of the other animes not shown here, or just to check out his work. I suggest you check Randazzle100 who has done a brilliant job of creating such awesome and fantastic artwork, in order to both help professional and fan artists. I hope these help!