Theoretical and experimental studies of the transverse dielectric properties of KH $_{2}$ PO $_{4}$ « A theory of the electric field gradient in KH $ _{2} $ PO $ _{4} $ -type crystals, based on the protonic E-mode » Unified model for the transverse electric susceptibility in KH$_2$PO$_4$ and NH$_4$PO$_4$ -type crystals
