On the Gyulai Hartly effect in single crystals of Potassium iodide at temperatures between 77 and 297 degree K - Hovi, Väinö 1913-1982; Mäntysalo, Esa; Ketolainen, Pertti (Suomalainen Tiedeakatemia, Helsinki: Annales Academiae Scientiarum Fennicae / A / 6, 1961)