“…Most crystals of the first group exhibit ferroelectric and other interesting polar properties which have been investigated by Pepinsky and Vedam (1959), Makita and Pepinsky (1962), Shuvalov et al (1967Shuvalov et al ( , 1970, Cevc et al (1967), Ivanov et al (1968 Aknazarov et al (1975), Chomnilpan et al ( , 1980 and Zagrai et al (1980). Most crystals of the first group exhibit ferroelectric and other interesting polar properties which have been investigated by Pepinsky and Vedam (1959), Makita and Pepinsky (1962), Shuvalov et al (1967Shuvalov et al ( , 1970, Cevc et al (1967), Ivanov et al (1968 Aknazarov et al (1975), Chomnilpan et al ( , 1980 and Zagrai et al (1980).…”