[1] Norrestam R, Nygrron M, Bovin J D. Structural investigations of new calcium-rare earth oxyborates with the composition Ca4RO(BO3). Chem. Mater., 1992, 4(3):737～743

[2] Iwai M, Kabayashi T, Furuya H et al.. Crystal growth and optical characterization of rare-earth (Re) calcium oxyborate ReCa4O(BO3)3(Re=Y or Gd) as new nonlinear optical material. Jpn. J. Appl. Phys., 1997, 36(3A):L276～L279

[3] Aka G, Kahn-Harari A et al.. Linear- and nonlinear-optical properties of a new gadolinium calcium oxoborate crystal, Ca4GdO(BO3)3. J. Opt. Soc. Am. (B), 1997, 14(9):L2238～L2247