"Evolution of amino acid frequencies in proteins over deep time: inferred order of introduction of amino acids into the genetic code".
بازبینی‌شده در ۲ اکتبر ۲۰۱۱.  «Evolution of Amino Acid Frequencies in Proteins Over Deep Time: Inferred Order of Introduction of Amino Acids into the Genetic Code» ‎(انگلیسی)‎.