1. V. Bessa, A. Porto and P.A. Zalesskii, Profinite genus of free products with finite amalgamation, https://arxiv.org/abs/2305.16054.
2. D. Haran, On closed subgroups of free products of profinite groups, Proceedings of the London Mathematical Society 55 (1987), 147–206.
3. D. Haran and M. Jarden, The absolute Galois group of a pseudo real closed field, Annali della Scuola Normale Superiore di Pisa. Classe di Scienze. Serie IV 12 (1985), 449–489.
4. D. Haran and M. Jarden, The Absolute Galois Group of a Semi-Local Field, Springer Monographs in Mathematics, Springer, 2021.
5. W. N. Herfort and L. Ribes. Torsion elements and centralizers in free products of profinite groups, Journal für die Reine und Angewandte Mathematik 358 (1985) 155–161.