When users search for they are almost exclusively referring to “Traveling Wave Antennas” by C. H. Walter (sometimes spelled Karl Walter or credited to Ohio State University). Published in the 1960s by McGraw-Hill, this monograph is part of the prestigious M.I.T. Radiation Laboratory Series (although some confusion exists with the later McGraw-Hill series).
When it comes to high-quality aspects of traveling wave antennas, several factors come into play: