Where can I learn more about EB2-era mercenaries?

[XDeath007]

* Not sure if this is the right place to post. Admins please let me know if it's not.

After reading Xenophon's Anabasis, I've become intrigued with the lives of mercenaries in the Classical/Hellenistic period. Can anyone recommend any good reads to further my knowledge on this topic? Much appreciated!

[Genava]

* Not sure if this is the right place to post. Admins please let me know if it's not.

After reading Xenophon's Anabasis, I've become intrigued with the lives of mercenaries in the Classical/Hellenistic period. Can anyone recommend any good reads to further my knowledge on this topic? Much appreciated!

For celtic mercenaries there is some good books/thesis in French. The best specialist is Luc Baray and I never have found an english-speaking equivalent:
Celtes, Galates et Gaulois – Mercenaires de l’Antiquité. By Luc Baray
Sociétés celtiques et mercenaires (VIIe Ier siècle av. J.-C.) La terre, le pouvoir et les hommes. By Luc Baray

There is a thesis about early gallic auxiliaries in French, available in pdf:
https://halshs.archives-ouvertes.fr/halshs-00749372

For more general review of the mercenaries, there is a book with a good reputation but I didn't read it:
Mercenaries of the Ancient World. By Serge Yalichev.

And about greek mercenaries, a book wrote by a true professor and historian but a bit more academic and hard to read:
Greek Mercenaries - From the Late Archaic Period to Alexander. By Matthew Trundle.