History of the Encyclopædia Britannica the criteria by which the articles were sorted were not obvious even to scholars, despite Dr. Adler's claims that the sorting followed naturally from the "Propædia's" outline of all knowledge. In 1985, the "Britannica" responded to reader requests by restoring the index as a two-volume set. The number of topics indexed by the "Britannica" has fluctuated from 500,000 (1985, the same as in 1954) to 400,000 (1989,1991) to 700,000 in the current 2007 print version. Presumably, this recent increase reflects the introduction of efficient electronic indexing, since the size of the encyclopedia has remained nearly constant at approximately 40 million
Software-defined data center According to some observers, software-defined data centers won’t necessarily eliminate challenges that relate to handling the differences between development and production environments; managing a mix of legacy and new applications; or delivering service-level agreements (SLAs). Software-defined networking was seen as essential to the software-defined data center, but it is also considered to be the “least mature technology” required to enable the software-defined data center. However, several companies, including Arista Networks, Cisco, Microsoft and VMware, market products to enable virtual networks that are provisioned, extended, and moved across existing physical networks. Several competing network virtualization standards already existed by 2012. Neutron,