 From the late 1950s, he was one of the first Mayanist scholars to give credence to the theories of the Russian linguist and ethnographer Yuri Knorozov concerning the phonetic and syllabic nature of the Maya script, which would later lead to breakthroughs in the script's decipherment.Kelley's landmark 1962 paper, "Phoneticism in the Maya Script", would provide important corroborating data of the phonetic interpretation of Maya glyphs, which ran counter to the then-prevailing view that the script lacked phonetic elements.In addition to his work on scripts and linguistics, he worked on calendrics and archaeoastronomy, particularly on application of archaeoastronomical data to the Maya calendar correlation problem.