This literature is remarkable for being in the vernacular (Old English) in the early medieval period: almost all other written literature was in Latin at this time, but because of Alfred's programme of vernacular literacy, the oral traditions of Anglo-Saxon England ended up being converted into writing and preserved. Much of this preservation can be attributed to the monks of the tenth century, who made – at the very least – the copies of most of the literary manuscripts that still exist. Manuscripts were not common items. They were expensive and hard to make. First, cows or sheep had to be slaughtered and their skins tanned. The leather was then scraped, stretched, and cut into sheets, which were sewn into books. Then inks had to be made from oak galls and other ingredients, and the books had to be hand written by monks using quill pens. Every manuscript is slightly different from another, even if they are copies of each other, because every scribe had different handwriting and made different errors. Individual scribes can sometimes be identified from their handwriting, and different styles of hand were used in specific scriptoria (centres of manuscript production), so the location of the manuscript production can often be identified.