Supplemental reference surface devices are provided for use in three-dimensional modeling of intra-oral scenes using identifiable positional characteristics from structured illumination or other techniques. Each reinforcing corner plate has two main portions angled to each other to form a substantially L-shape, and two wing portions projecting respectively from the main portions. The transfer of steam through the shroud holes results in the relief of the pressures gradient on the surface of the shroud and prevents the formation of metal oxide, salt and other deposits on the inner surfaces of the shroud. Optionally, the clothing holder may be configured in a stored-use or transport state in which the articles are securely stored in a folded configuration while a backpack portion of the combination backpack and clothing holder is being worn. A first UE sends a request for transferring media streams of a multimedia session to an AS, where the request carries the ID of a third UE and the media type of media streams requested to be transferred; and the third UE establishes media streams of the media type with a second UE under the control of the AS.