Support the importance of your problem
Discuss previous work on modeling/analysis in the area
Have the statistical analysis and results from research being done
Cover technical aspects of the methods
These sources should present a comprehensive review of the historical and current literature in the topic area. Address any key issues: political, social, legal, ethical implications the literature reports. What is projected if nothing is done; what has been tried? Insure that if there are pros and cons of a topic/issue, that your sources explore holistically a review of the literature reflecting alternative positions.