JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, vol. 36, no. 4A, page. 2134 - 2135, 1997-04
INSTITUTE OF PHYSICS CONFERENCE SERIES, vol. 145, page. 999 - 1002, 1996-01
JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, vol. 37, no. 9A, page. 4818 - 4821, 1998-09