Boy, I., Schäfer, G., & Kniep, R. (2001). Crystal structure of sodium iron (II) diaqua catena-[monoboro-diphosphate] monohydrate, NaFe(H2O)2[BP2O8] · H2O, and of potassium iron(II) diaqua catena-[monoboro-diphosphate] hemihydrate, KFe(H2O)2[BP2O8] · 0.5H2O. Zeitschrift für Kristallographie - New Crystal Structures, 216, 13-14. doi:10.1524/ncrs.2001.216.14.13.