Add one of the pair of letters below the equals sign to the left-hand side of the equation and the other of the pair to the right-hand side, rearranging the four letters on each side to make "nothing equals nothing".
I write mathematics, logic, and lateral thinking puzzles for The Daily Telegraph (UK). My books include Brain Busters (Dover: 2003) and Challenging Logic Puzzles - Mensa (Sterling: 2003). I have also acted as consultant for BBC TV Mindgames. There are several projects I am working on: a new puzzle book is being prepared, I am organising an exhibition of my visual lateral puzzles in London, and the Shakespeare authorship problem http://barryispuzzled.com/shakpuzz.pdf for free e-book. For puzzle solutions email firstname.lastname@example.org