{HEAD ~ Reducing agent} can be conveyed back from the delivery device to the reservoir via {TAIL ~ a return line} 
conveyed back via
{ HEAD ~ Reducing agent } can be conveyed back from the delivery device to the reservoir via { TAIL ~ a return line }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL