d ref. = Eimerl, Ferroelectrics vol. 72, 95 (1987)
  Nikogosyan D. Nonlinear optical crystals.. a complete survey (Springer, 2005)(ISBN 0387220224)(430s).pdf
    | 0   0   0  0.39   0     0   |
  d=| 0   0   0   0    0.39   0   |
    | 0   0   0   0     0    0.39 |