The date of the University of Bologna's founding is uncertain, but believed by most accounts to have been 1088. The university was granted a charter ("Authentica habita") by Holy Roman Emperor Frederick I Barbarossa in 1158, but in the 19th century, a committee of historians led by Giosuè Carducci traced the founding of the University back to 1088, which would make it the oldest continuously-operating university in the world. However, the development of the institution at Bologna into a university was a gradual process. Paul Grendler writes that “it is not likely that enough instruction and organization existed to merit the term "university" before the 1150s, and it might not have happened before the 1180s.”