Barthel's "Grundlagen zur Entzifferung der Osterinselschrift"
"Grundlagen zur Entzifferung der Osterinselschrift" is Thomas Barthel's Habilitationsschrift. Published in 1958, it is one of the cornerstone documents in work on rongorongo. Its most influential aspect was—is—the tracings of the rongorongo corpus and the numbering scheme he devised for the glyphs.
This document has long gone out of print, and it is not easy to come by, if you don't have a good library. The work is quite multi-lingual, mixing German, French, Spanish, English, Latin(!), as well as Rapanui/Tahitian. The main text is in German.
The file linked below has been OCRed and proofread, but please beware of errors. Check with the original (or the scans) in case of doubt.
The two files linked below contain materials which cannot be OCRed. The first contains Barthel's tables of glyph forms. The second includes Barthel's tracings of the rongorongo. These are the originals of the material found throughout this website.
Below I am also providing scans of Barthel's thesis. These are the originals that I used for the OCR. Since these are image files, the files are very heavy (30-50 MB each).