However none of these "undisclosed sources" mentioned by Prisuta, Madden or Judge have ever come forward to the media.
While leaning heavily on the sources already mentioned, Houbraken also consulted local history books of various cities in the Netherlands.
Accordingly, Islamic jurisprudence has changed little for centuries and is based fundamentally on the four sources mentioned above.
Others of the sources mentioned above say the same.
A list of sources mentioned throughout the book can be found on pages 159 and 160.
In addition to the sources mentioned in the article:
Whether any of the sources mentioned above represent the original form of the work is also doubtful.
All electronic sources mentioned in this article were retrieved in the spring of 2010.
While the sources mentioned are far-flung, they are meant only as suggestions.
Many such books are now lost works and remembered only by his references, much like the lost sources mentioned in the work of Vitruvius a century earlier.
