The pitfalls of maintaining a manual sitemap
Manually administering a sitemap is not without its problems. Not only do you have to add the declaration manually to both the source file and the sitemap. The best way that I have found is to copy and paste between the two files. However, if you have a typo in either it will cause an error when Google attempts to index it.
A case in point is my page on historical Societies, I made a declaration with the file name historial.html, this should have been historical.html