No comma is needed. For example: In my backyard and on my back porch are two places where I enjoy relaxing.
Executive order 9066 dictated the relocation of Japanese-Americans during WW2. It was a real even during the hysteria of WW2 whilst works of fiction are made up.
The part of the sentence that tells "who" or "what" the sentence is about is the subject.
To whom it may concern, In regards to the Memorial Day Fiasco aboard your cruise ship, star princess we would first offer our sincere apology, for our part in the mishap. While we do not plan on taking legal action against you or the Maroccan authorities, we are requesting parties to avoid another Waterloo captain. Johnson may just want to remember a key items.
