Phys Rev B Condens Matter
January 1993
Phys Rev B Condens Matter
December 1992
Phys Rev B Condens Matter
September 1991
Phys Rev B Condens Matter
February 1991
Phys Rev B Condens Matter
September 1989
Phys Rev B Condens Matter
March 1989
Phys Rev B Condens Matter
July 1988
Phys Rev B Condens Matter
February 1985
Phys Rev B Condens Matter
February 1985