The advantages of heterogeneity and concurrency of the distributed system are thus extended to {HEAD ~ its switched communications links} with {TAIL ~ external switched networks} 
The advantages of heterogeneity and concurrency of the distributed system are thus extended to { HEAD ~ its switched communications links } with { TAIL ~ external switched networks }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL