This Data Book has potential to be a magnificent reference book. In the mid-1970s I bought an edition of this book, which has been a valuable guide to me and my work in the interim period. Late in the year 2000 I bought this book again (through 'Amazon'), keen to be up-to-date with the latest scientific knowledge, and I was disappointed to see that there had been no change whatsoever in the book's content in the interim period. This cannot be so in practice, since many definitions and units have changed. In Radioactivity alone, previous units such as Curies, Rads and Rems, as defined in the book, have been superseded by (among other things) bequerels and sieverts. Admittedly the mathematical formulae and universal contants listed would not have changed since the 70s, but one would expect certain details to be updated from time to time. This book should normally get five stars, but as it is not up to date, it only gets three from me. At least the year of last impression is correct!