The short fibers may be made of {HEAD ~ a single crystal} such as {TAIL ~ whisker} or of a polycrystal 
such as
The short fibers may be made of { HEAD ~ a single crystal } such as { TAIL ~ whisker } or of a polycrystal
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH