While the hypothetical scenarios are the most important background resources, you may also wish to consult the following materials.
The U.S. Code and The Constitution
(These links will take you to the Legal Information Institute at Cornell Law School)
3 U.S. Code CHAPTER 1—PRESIDENTIAL ELECTIONS AND VACANCIES
§ 5. Determination of controversy as to appointment of electors
§ 9. Certificates of votes for President and Vice President
§ 15. Counting electoral votes in Congress
12th Amendment [Election of President and Vice-President (1804)]
20th Amendment [Presidential Term and Succession (1933)]
Other Resources
Foley, Edward B., Preparing for a Disputed Presidential Election, 51 Loyola University Chicago Law Journal 309 (2019).
Foley, Edward B., APPENDIX to Preparing for a Disputed Presidential Election, 51 Loyola University Chicago Law Journal 309 (2019).
Ad Hoc Committee for 2020 Election Fairness and Legitimacy (convened by Richard L. Hasen), Fair Elections During a Crisis: Urgent Recommendations in Law, Media, Politics, and Tech to Advance the Legitimacy of, and the Public’s Confidence in, the November 2020 U.S. Elections (April 2020).
Supreme Court opinion of April 6, 2020 in RNC vs DNC.