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REFERENCES: |
    M. Simon, F. Mersch, C. Kuper, S. Mendricks, S. Wevering, J. Imbrock, E. Krätzig.
    Refractive indices of photorefractive bismuth titanate, barium-calcium titanate, bismuth germanium oxide, and lead germanate.
    <a href="https://doi.org/10.1002/1521-396X(199702)159:2<559::AID-PSSA559>3.0.CO;2-0"><i>Phys. Stat. Sol.</i> <b>159</b>, 559-562 (1997)</a>
COMMENTS: |
    Polarization parallel to b-axis. 21 °C.
DATA:
  - type: formula 2
    wavelength_range: 0.45 0.70
    coefficients: 1.176 4.536 0.06182