You may need to download the latest version of Adobe Reader .

Most of the files here—almost all of them—are in the Portable Document Format designed by Adobe.

Readers wanted the stable format and easy printing of the .pdf file format. For most documents, which are generated from original text files, .pdf does not add much to the file size. Sometimes the files get smaller.

Other material, especially book and whole journal issues, have been created by scanning images of paper originals. We are then faced with a choice. Do we do optical character recognition (OCR), which adds a lot of extra work, is error prone, and loses the original formatting, or do we simple process the graphic images into .PDF files? For most material we chose the latter. The result is fidelity to the original, but much larger files.

To compensate somewhat, we have used the highest level of compression available with Adobe Acrobat 6. But this means that the Adobe Reader version 6 (available free from www.adobe.com) is needed to read the files. We have also run Adobe's Paper Capture on the files. This is an OCR process that creates a word index that is saved along with the images in the .pdf file. This makes the files searchable using Adobe Reader. Be aware, however, that Paper Capture is error prone and misidentifies some words, which are then wrong in the index.