http://djm.cc/library/ contains a number of very interesting works including that all time classic of Silvanus P Thompson's Calculus Made Easy. There are a number of works which are not directly relevant to the hobby whether they are fit for family viewing I do not know. You will need to make your own assesment of the copyright situation. _________________________________________________________________ Fancy some celeb spotting? https://www.celebmashup.com MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.