After Bishop had assigned about 4,000 CODEN, the four letter CODEN system was further developed since 1961 by L.E. Kuentzel at the American Society for Testing of Material (ASTM).
Setelah Bishop menugaskan sekitar 4,000 CODEN, empat huruf sistem CODEN dikembangkan lebih lanjut sejak tahun 1961 oleh Dr. Kuentzel di American Society for Testing of Material (ASTM).