Nit: G7 denotes a G dominant 7 (i.e. natural 3rd, flat 7th), not a G minor 7. G minor 7 (flat 3rd, flat 7th) is abbreviated Gm7 or G-7. (In my experience, the "Gm7" form is common in "official" printed guitar & piano songbooks, while G-7 is common in jazz lead sheets and fakebooks.)