The eBooks found here are almost without exception taken from scan copies of the original books held in University libraries. When we get them, they have been processed by OCR software to extract the content.
When we acquire them, they are FULL of OCR errors. Each page in each book has to be carefully compared page by page with the scans and errors corrected for readability and accuracy. It can take 3-7 manhour days to do this per book and 1-2 manhour days to HTML format them for the web and produce the various eBook editions for download.