And again, this study did not consider the Koran as "violent literature".
"The mosques surveyed contained a variety of texts, ranging from contemporary printed pamphlets and handouts to classic texts of the Islamic canon. From the perspective of promoting violent jihad, the literature types were ranked in the survey from severe to moderate to nonexistent. The texts selected were all written to serve as normative and instructive tracts and are not scriptural. This is important because a believer is free to understand scripture literally, figuratively, or merely poetically when it does not have a normative or legal gloss provided by Islamic jurisprudence.
The moderate-rated literature was authored by respected Shari'a religious and/or legal authorities; while expressing positive attitudes toward violence, it was predominantly concerned with the more mundane aspects of religious worship and ritual. The severe material, by contrast, largely consists of relatively recent texts written by ideologues, rather than Shari'a scholars, such as Abul Ala Mawdudi and Sayyid Qutb. These, as well as materials published and disseminated by the Islamist Muslim Brotherhood, are primarily, if not exclusively, aimed at using Islam to advance a violent political agenda."