Lessons In Electric Circuits -- Volume IV (Digital) - Chapter 11
3 Bit Counter JK Flip flop | Tinkercad
How to design a synchronous counter 4 bit using JK flip flop that can count up even numbers from 0 to 14, and count down odd numbers from 15 to 0 in 1 system - Quora
JK Flip Flop Circuit Diagram in Proteus - The Engineering Projects
Conversion of Flip-flops from one flip-flop to Another