Following the takeover of Timbuktu by MNLA and the Islamist group Ansar Dine, it was returned to the List of World Heritage in Danger in 2012. In May 2012, Ansar Dine destroyed a shrine in the city and in June 2012, in the aftermath of the Battle of Gao and Timbuktu, other shrines, including the mausoleum of Sidi Mahmoud, were destroyed when attacked with shovels and pickaxes by members of the same group. An Ansar Dine spokesman said that "all" shrines in the city, including the 13 remaining World Heritage sites, would be destroyed because they consider them to be examples of idolatry, a sin in Islam. These acts have been described as crimes against humanity and war crimes. After the destruction of the tombs, UNESCO created a special fund to safeguard Mali's World Heritage Sites, vowing to carry out reconstruction and rehabilitation projects once the security situation allows. Timbuktu was a world centre of Islamic learning from the 13th to the 17th century, especially under the Mali Empire and Askia Mohammad I's rule. The Malian government and NGOs have been working to catalog and restore the remnants of this scholarly legacy: Timbuktu's manuscripts. Timbuktu's rapid economic growth in the 13th and 14th centuries drew many scholars from nearby Walata (today in Mauretania), leading up to the city's golden age in the 15th and 16th centuries that proved fertile ground for scholarship of religions, arts and sciences. To the people of Timbuktu, literacy and books were symbols of wealth, power, and blessings and the acquisition of books became a primary concern for scholars. An active trade in books between Timbuktu and other parts of the Islamic world and emperor Askia Mohammed's strong support led to the writing of thousands of manuscripts. Knowledge was gathered in a manner similar to the early, informal European Medieval university model. Lecturing was presented through a range of informal institutions called madrasahs. Nowadays known as the University of Timbuktu, three "madrasahs" facilitated 25,000 students: Djinguereber, Sidi Yahya and Sankore. These institutions were explicitly religious, as opposed to the more secular curricula of modern European universities and more similar to the medieval Europe model. However, where universities in the European sense started as associations of students and teachers, West-African education was patronized by families or lineages, with the Aqit and Bunu al-Qadi al-Hajj families being two of the most prominent in Timbuktu – these families also facilitated students is set-aside rooms in their housings.