Gates made the appeal at a joint press conference with his Italian counterpart Ignazio La Russa.
Of the 700-odd officially published photo portraits of late Chairman Mao Zedong, more than 400 were taken by photographer Hou Bo.
China Thursday lodged a complaint with the WTO over the EU's anti-dumping duties on Chinese leather shoe imports.
Marilyn Monroe is shown in this December 1961 photo taken in New York City in this photo released to Reuters February 5, 2010.
Paris Hilton seen filming a commercial for an Israeli Lottery in Midtown, New York City.
Zhang Yi, a 28-year-old imagined her boyfriend's proposal to be romantic.