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3. M. Svoboda, Contrast Agents [in Czech], Prague (1964), p. 174.
4. N. S. Maleev, in: Handbook on Authorization of Contrast Agents for use in the Bulgarian People's Republic [in Bulgarian], Sofia (1967), p. 64.
5. S. Barke, Radiographic Contrast Agents [in German], Leipzig (1970), p. 290.