I am getting ready to sell my first prints of some photos I took at a public event in town, some (but very few) of which are portraits of strangers. Can I (legally) sell photos of someone I don't know / who doesn't know me? It may just be that the portraits are included in a collage of photos, but I'd like to sell them individually if I am able to. The event was very packed and moving fast, so I couldn't stop these people to ask them this question specifically. Most of my photos were very spur-of-the-moment; I didn't even look at them until I got home later that day. Thanks for the help!