Sentence:  They marked the beginning of each scroll with their <WSD>"protocol</WSD>", a practice that continued in the papyrus trade in the Byzantine Empire [...] into the Islamic period, when there were bilingual <WSD>protocols</WSD> in Greek and Arabic. 
Meaning of the word marked with <WSD> tags:  The first leaf of a roll of papyrus, or the official mark typically found on such a page. (from 19th c.)