2616: Hypertext Transfer Protocol -- HTTP/1.1 Internet Engineering Task Force, 1999. (See http://www.ietf.org/rfc/rfc2616.txt.) URI RFC 3986: Uniform Resource Identifier (URI): Generic Syntax (See http://www.ietf.org/rfc/rfc3986.txt.) MARS Mars . Description in Wikipedia (See http://en.wikipedia.org/wiki/Mars.) METRE Metre . Description in Wikipedia. (See http://en.wikipedia.org/wiki/Metre.) SI The NIST Reference on Constants, Units and Uncertainty (See http://physics.nist.gov/cuu/Units/.)