{HEAD ~ The medium} may be used for serum free culture or supplemented with {TAIL ~ low levels} of serum 
supplemented with
{ HEAD ~ The medium } may be used for serum free culture or supplemented with { TAIL ~ low levels } of serum
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH