There are a number of books on British railway accidents which provide aid in the systematic study of the causes and effects of accidents, and their prevention. There are common themes in many accidents (see Classification). Key books are listed here to avoid repeating them for each individual accident. The list below does not include books on individual accidents; for these, see Tay Bridge, Quintinshill, Harrow and Moorgate. An extremely valuable source now on the Internet is the Railways Archive compilation of official Railway Inspectorate Accident Reports - see "External Links" below.