After the shift of Javanese power to eastern Java, it had been quiet from Central Java for several centuries concerning Javanese literature until the 16th century. At this time, the centre of power was shifted back to Central Java. The oldest work written in modern Javanese language concerning Islam is the so-called "Book of Bonang" or also "The Admonitions of Seh Bari". This work is extant in just one manuscript, now kept in the University of Leiden as codex Orientalis 1928. It is assumed that this manuscript originates from Tuban, in eastern Java and was taken to the Netherlands after 1598. However, this work is attributed to Sunan Bonang, one of the nine Javanese saints who spread Islam in Java and Sunan Bonang came from Bonang, a place in Demak Regency, Central Java. It can be argued that this work marked the beginning of Islamic literature in the region.