These can be in parallel or in sequence, and a set of parallel modules can also be in sequence with {HEAD ~ a subsequent set} of {TAIL ~ parallel modules} 
of
These can be in parallel or in sequence , and a set of parallel modules can also be in sequence with { HEAD ~ a subsequent set } of { TAIL ~ parallel modules }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL