{HEAD ~ The method} for the cultivation of primary cells may be one step in {TAIL ~ a method} for the amplification of viruses, wherein the cells are then infected with a subject virus and the infected cells are cultivated in serum free medium until progeny virus is produced 
{ HEAD ~ The method } for the cultivation of primary cells may be one step in { TAIL ~ a method } for the amplification of viruses , wherein the cells are then infected with a subject virus and the infected cells are cultivated in serum free medium until progeny virus is produced
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