 Complete the following phrase:  The series has been frequently criticised for omitting mention of controversial US foreign policies, due to limitations on the declassification of historical documents. In the late 1980s and early 90s, growing concerns over the accuracy of the seriess coverage of the Cold War era led to a 1991 Congressional statute to provide the series with a legal mandate for timeliness and comprehensiveness. Notable alleged incidents believed to be omitted or censored include the United States governments covert involvement in the 1953 Iranian coup détat, the 1954 Guatemalan coup détat, the 1960 assassination of Patrice Lumumba, and the 