Levy
Biochimica et Biophysica Acta, 1954 , vol. 15, p. 589

Ramachandran et al.
Analytical Chemistry, 1955 , vol. 27, p. 1734,1735
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Sjoequist
Arkiv foer Kemi, 1957 , vol. 11, p. 129,130,132
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Edman
Acta Chemica Scandinavica (1947-1973), 1950 , vol. 4, p. 277,281