Thanks to the Center for Japanese Studies Publications, The Three Jewels : a study and translation of Minamoto Tamenori's Sanbōe by Edward B. Kamens is now available in its entirety online. I've loved Kamens' translation of the the Mahāsattva Jātaka for quite a while now, but it wasn't until recently that I discovered the treasure trove of a tome that it's part of...
A searchable web version: http://quod.lib.umich.edu/c/cjs/1077715.0001.001/--three-jewels-a-study-and-translation-of-minamoto-tamenoris?view=toc
The full book in PDF format: http://quod.lib.umich.edu/cgi/p/pod/dod-idx/three-jewels-a-study-and-translation-of-minamoto-tamenoris.pdf?c=cjs;idno=1077715.0001.001
From the Introduction: