Which type of source is NOT typically included in a literature review?

Which of the following is NOT a reason behind the decline of trade unions?

A) Globalization of individualism B) Public perceptions of unions C) Growth in the power of the manufacturing economy D) Political change

Of the following events, which would political scientists consider least likely to have a generational effect on people's political outlooks?

a. the Great Depression b. the civil rights movement c. the 9/11 terrorist attacks d. the incidence of childhood leukemia