“…[47] Very recently it has been pointed out that surface creases in elastic films are analogous to Kosterlitz-Thouless instabilities. [48] Other authors have shown [49,50] that Kosterlitz-Thouless melting within n-vertex Potts model descriptions requires vertices with n>4 and does not arise from the threefold and fourfold vertices considered by Srolovitz and Scott [51] and characteristic of BaTiO3, PbTiO3, and PZT films considered here. We should note that our analysis is supported by a recent work by Sigov who suggested that defects in ferroelectrics can be correlated and comply with the KosterlitzThouless model.…”