As others have stated, there are no absolute authorities or rules on English punctuation. However, there are certain guidelines that are helpful. Rather than putting my foot in my mouth by trying to list or explain such guidelines, I point you to two useful resources. - The Chicago Manual of Style https://books.google.com/books/about/The_Chicago_Manual_of_Style.html?id=4xJIAQAAIAAJ&source=kp_cover&hl=en see also http://en.m.wikipedia.org/wiki/The_Chicago_Manual_of_Style - Elements of Style https://books.google.com/books/about/Elements_of_Style.html?id=K23rAgAAQBAJ&source=kp_cover&hl=en Remeber that the above are only two author's opinions. Others here can probably point to other good resources. I specifically do not recommend _**Eats, Shoots and Leaves**_, because Ms. Truss does not distinguish between hyphens, en-dashes, and em-dashes, instead calling them all "dashes". Just remember also that opinions vary. See, for, other questions about hyphens on this forum.