We aim to keep the cost of our books as low as possible. Our aim is spread knowlege, not to make money.                                                                                                                                                                            However, when our books are bought through commercial outlets, they may cost more than the prices shown here. It is only reasonable that such places require to make a profit, otherwise they could not continue.                                                                                                                                                                                                                            If you have any question about where you can buy our books, or is you wish to get them directly from us, please do contact us.