Other later historical works, particularly those of the 3rd and 4th century of the Islamic calendar, are also of considerable importance in mapping Muhammad's life in the city. These include the early biographies of Muhammad ("seerah"), particularly those written by Ibn Ishaq (–767 CE) and Ibn Sa'd (–845 CE), and quotes attributed to Muhammad in hadith literature, compiled by Islamic scholars such as Al Bukhari (–870 CE) and Muslim ibn Hajjaj (–875 CE) which provide further information on his life. The earliest surviving "seerah" is the ""Sīrah Rasūl Allah"" by Ibn Ishaq. Although the original is lost, portions of it survive in the recensions of Ibn Hisham and al-Tabari. Many historians accept the accuracy of these biographies, though their accuracy is unascertainable. According to William Montgomery Watt, in the legal sphere, it would seem that sheer invention could have very well happened. In the historical sphere, however, aside from exceptional cases, the material may have been subject to "tendential shaping" rather than being completely fabricated.