1. The 8051 Micro-controller Architecture, programming & Applications By: Kenneth J. Ayala
2. The 8051 Microcontroller and Embedded Systems By: MD Ali Mazidi
3. Practical transistor circuit design and analysis By: GERALD E. WILLIAMS
4. Programming and Customizing the 8051 Micro-controller By: Myke Predko
5. The concepts and Features of Micro-controllers - By: Raj Kamal