Rose Kennington, Pennsylvania. Keep it up. It isn't easy. I haven't solved it yet. Only seemed to have half of it and then a steel barrier which I can't pass.
Plain substitutions are all right, but too darn easy and common.
I might add that I find very little difficulty in solving The Third Degree problems. I am a member of The Shadow Club, and I also read Doc Savage and Pete Rice Magazines, though I think The Shadow Magazine is best. Keep up the good work. William J., Pennsylvania. I have never written to another company before.