Dear All, When reading the lecture notes about DFPT, I met following similar terms: "star of q", " q star", I was wondering what are they referred to. Do they mean "q*"? Thank you. Andy -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120321/8f2ec076/attachment.htm