Phys Rev B Condens Matter
July 1996
Phys Rev B Condens Matter
July 1993
Phys Rev B Condens Matter
March 1993
Phys Rev B Condens Matter
August 1992
Phys Rev B Condens Matter
February 1992
Phys Rev B Condens Matter
August 1991
Phys Rev B Condens Matter
May 1991
Phys Rev B Condens Matter
April 1990
Phys Rev B Condens Matter
April 1989
Phys Rev B Condens Matter
April 1986
Phys Rev B Condens Matter
January 1986