I am looking for two facts about free pro-$p$ groups, and will be glad to receive some reference or suggestions
For convenience reasons, I'll post my questions in two different messages:
In "The structure of groups of prime power order"/Leedham-Green , it is written that there is a normal form of writing the elements in a free pro-$p$ group as a product of basic commutators. Although I am familiar with the collection process in finite groups, I can't understand what is this "normal" form in the free pro-$p$ context.
Does someone have an idea? Can someone tell me where can I find this "normal" form?