DIY Free Printable Science Valentines from Evil Mad Scientist. The ones with equations are from their 2013 collection and symbol Valentines’ cards are from their 2014 collection.
DIY Inspiration: “Queen of hearts/Suicide King” 2013 by Elmo Hood here. I’ve seen this in a few places with no mention of the artist/original source.
DIY 3D Party Invitations or Holiday Cards Tutorial from Manda Townsend here. This is such a good idea – corrugated cardboard and sheet protectors.