VACUUM, vol. 42, no. 8-9, page. 555 - 560, 1991-01
VACUUM, vol. 44, no. 5-7, page. 697 - 699, 1993-05
VACUUM, vol. 47, no. 6-8, page. 807 - 809, 1996-06
VACUUM, vol. 47, no. 3, page. 297 - 306, 1996-03
VACUUM, vol. 42, no. 7, page. 457 - 462, 1991-01