{HEAD ~ The internal mechanisms} may comprise {TAIL ~ a wide variety} of actuation systems for extending and retracting the writing implement, including a cam actuation assembly, an edge slide actuation assembly, a gravity actuation assembly, a pressure actuation assembly and a push button actuation assembly 
comprise
{ HEAD ~ The internal mechanisms } may comprise { TAIL ~ a wide variety } of actuation systems for extending and retracting the writing implement , including a cam actuation assembly , an edge slide actuation assembly , a gravity actuation assembly , a pressure actuation assembly and a push button actuation assembly
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH