I have been looking at the various modules available to make this shape and I have found deep in my files a post from Jeannine Mosely dated July 11th 1994 describing - and illustrated using ASCII diagrams! - her version.
In a note she states that the same module was independently discovered by Roberto Morassi and appears in 'a book by Fuse on international modular origami'. I wonder if anyone can help me identify the title of this book and its publication date? Thank you. Dave
