About this book: "Letters of Medieval Jewish Traders", and especially about this source of information:
> Shlomo Goitein used the documents that were serendipitously discovered in the geniza of the Cairo synagogue
I'm still waiting for a proper "inclusion" of their contents in the "main" historical discourse, it's a pity that there aren't much many historians going through them and using their contents. From the dedicated wiki page [1]:
> The Cairo Geniza, alternatively spelled the Cairo Genizah, is a collection of some 400,000[1] Jewish manuscript fragments and Fatimid administrative documents that were kept in the genizah or storeroom of the Ben Ezra Synagogue in Fustat or Old Cairo, Egypt. (...) comprise the largest and most diverse collection of medieval manuscripts in the world.