1. Fred Cohen. 1995. Introductory Information Protection (1st. ed.). Fred Cohen. 1995. Introductory Information Protection (1st. ed.).
2. Howard Poston and Keshav Dhandhania. 2001. The Playfair Cipher (2001). Retrieved May 5 2019 from https://www.commonlounge.com/discussion/350ac6f155ba48ecbd0fb8fd38e2f205 Howard Poston and Keshav Dhandhania. 2001. The Playfair Cipher (2001). Retrieved May 5 2019 from https://www.commonlounge.com/discussion/350ac6f155ba48ecbd0fb8fd38e2f205
3. Lexico. Which Letters In The Alphabet Are Used Most Often? Retrieved from https://www.lexico.com/en/explore/which-letters-are-used-most Lexico. Which Letters In The Alphabet Are Used Most Often? Retrieved from https://www.lexico.com/en/explore/which-letters-are-used-most
4. Information Security using Adaptive Multidimensional Playfair Cipher;Bhat Krishnaraj;International Journal of Advanced Research in Computer Science, 8 (5),2017
5. A Modified Circular Version of Playfair Cipher