Table: election_results_1968_2
Columns: district
incumbent
party
first_elected
result
candidates

Question: What district did Joe Waggonner belong to?
SQL: SELECT "district" FROM election_results_1968_2 WHERE "incumbent" = 'Joe Waggonner'

Question: What is the name of the incumbent who was first eleccted in 1940?
SQL: SELECT "incumbent" FROM election_results_1968_2 WHERE "first_elected" = 1940