Although I used many articles and websites online. My main sources of information were from various books and textbooks. My main sources of information that helped me learn about optical illusions were:
101 Amazing Optical Illusions by Terry Jennings
Optical Illusion Magic-Visual Tricks and Amusements by Michael A. DiSpezio
Visual Magic by David Thompson
Now You See It-Now You Don’t by Seymour Simon
The Little Giant Book of Optical Illusions by Keith Kay
Masters of Deception:Escher, Dali & the Artists of Optical Illusion by Al Seckel