For those who are interested in an extremely user-friendly electronic version of the now out-of-print four-volume Ordinary Form Missale Romanum cum lectionibus, a site called presbyter.eu has made it available in four djvu-format files, with a supplement file noting changes ("additiones et mutationes") to the original edition. (I'll admit I had never heard of the djvu format, but it took only a few minutes to download the free WinDjView software.) Once I was able to open these files, I was blown away by the labor that has been done to organize the material. If you are utilizing the modern Missale Romanum in Latin or doing any scholarly research on it whatsoever, you will definitely want this resource. (h/t Fr. Z)
