Hensel, N., Franz, G., Riedl, M., Gottschalk, M., Wunder, B., Galbert, F., Nissen, J. (2007): Polymorphism and solid solution in the system SiO2-AlPO4(-H2O): a review and new synthesis experiments up to 3.5 GPa and 1573 K. - Neues Jahrbuch für Mineralogie Abhandlungen, 184, 2, 131-149.https://doi.org/10.1127/0077-7757/2007/0087