Im sure you can find plenty of reference in “Supertraining” and “Science and Practice of Strength Training.” If I get a chance later one maybe I will take a look for you.
CNS fatigue and its affects are still very poorly understood.
“The exact mechanism for CNS fatigue remains largely unknown but it appears that acute CNS fatigue may occur as a result of decreased reflex sensitivity and or through less than optimal output from the motor cortex”
It is assummed that training volume and intensity may play a role in this decreased refelex sensitivity, however a lot more research is required before we fully understand CNS fatigue and its implications to training.