FERROELECTRICS, vol. 259, no. 1-4, page. 9 - 14, 2001-01
JOURNAL OF APPLIED PHYSICS, vol. 92, no. 8, page. 4820 - 4824, 2002-10-15
JOURNAL OF APPLIED PHYSICS, vol. 90, no. 9, page. 4407 - 4410, 2001-11-01