The paper on two-level patterns considers the method used to produce these in Persia. This is more complex than the simple use of overlays that has been used prevously in this collection. The detail of such patterns may not be apparent from the small graphics - the larger PDF file needs to be inspected.
A major planned addition is nearly complete to add dates to those Islamic patterns for which information is available, for details see Dates of Islamic patterns. Also, the references to a pattern are now ordered giving the ones with the earliest date first. From an example, see Bourgoin, Plate 67.