The free-market administration of patents as described here differs in another respect from the current system, as well as the system envisioned by Ayn Rand (). The same (or virtually the same) invention may be developed by two or more creators independentlythat is, with each creator having no prior knowledge of the other's work or its results. Under the system historically used in the United States, only the first creator to file at the patent office is allotted exclusive patent rights. In perhaps the most famous application of this rule, Alexander Graham Bell obtained an exclusive patent on the telephone, while Elisha Gray, developing the same invention independently but arriving at the U. S. Patent office two hours later, was denied all rights to his creation (more information). In the free market, however, any attempt to deprive subsequent creators of the full use of their own workincluding any conditions attaching to sales of their products, which they could register as patentswould constitute a violation of their rights. On the other hand, a second creator might encounter a greater legal burden of proof if his or her independent origination were challenged in court.