CHEN CHUANG-TIAN. AN IONIC GROUPING THEORY OF THE ELECTRO-OPTICAL AND NON-LINEAR OPTICAL EFFECTS OF CRYSTALS (Ⅲ)——A THEORETICAL CALCULATION OF THE ELECTRO-OPTICAL AND OPTICAL SECOND HARMONIC COEFFICIENTS FOR LiNbO3, LiTaO3,KNbO3, AND BNN CRYSTALS BASED ON A DEFOJ. Acta Physica Sinica, 1977, 26(6): 486-499. DOI: 10.7498/aps.26.486