The U.S. Census website (https://www.census.gov/geo/maps-data/data/ua_rel_download.html) provides several types of relationships:
-Urban area to MSA (metropolitan statistical area) relationships
-Urban area to place relationships
-MSA to principal city relationships
I can't seem to find MSA to place relationships. Is there a direct source for this? If not, how can I derive them from existing data?