Here's a group of links giving additional information and reference materials I find interesting or useful. I've maintained many of these charts and tables as adjuncts to my professional activities over the years. I have found them useful in my development work. Remember that this information has been gleaned from a variety of sources, and undoubtedly contains some errors. Please do not use these data where such errors could result in a hazardous situation. I will not accept responsibility for any harm resulting from the use of these data.