I think you've cracked it, djawhujc, except that the preamble says, of the rectangle, that it should be "treated symbolically using only initial cells." I take the "only" to mean that we put the Greek letters in the nine "initial" cells, as you suggest, but then erase the other 40 cells, just as we are required to do with the remaining 42 cells of the square. Or am I reading too much into it? Amazing that while the previous week's crossword didn't produce a single forum comment, this one's provoked no less than 52! If Shackelton has been reading it, he must be laughing his head off.