▁for ▁dec ades ; ▁perm al inks ▁usually ▁do ▁not ▁change ▁the ▁URL ' s ▁domain , ▁and ▁are ▁intended ▁for ▁use ▁on ▁times cal es ▁of ▁years . ▁ ▁Perm al inks ▁and ▁versions ▁ ▁Many ▁blog ging ▁and ▁content ▁management ▁systems ▁do ▁not ▁support ▁version ing ▁of ▁content , ▁that ▁is , ▁if ▁an ▁entry ▁is ▁updated , ▁a ▁uniqu ely ▁accessible ▁version ▁is ▁not ▁created . ▁ ▁Thus , ▁in ▁the ▁context ▁of ▁these ▁systems , ▁a ▁perm al ink ▁may ▁refer ▁to ▁different ▁content ▁over ▁time . ▁ ▁In ▁the ▁context ▁of ▁systems ▁that ▁support ▁version ing , ▁such ▁as ▁most ▁w ik is , ▁a ▁perm al ink ▁is ▁commonly ▁understood ▁as ▁a ▁link ▁to ▁a ▁specific ▁version . ▁Here , ▁both ▁the ▁link ▁itself ▁and ▁the ▁resource ▁it ▁refers ▁to ▁should ▁not ▁change ▁over ▁time . ▁ ▁Media Wik i , ▁the ▁software ▁that ▁runs ▁Wikipedia , ▁supports ▁this ▁type ▁of ▁permanent ▁link . ▁ ▁In ▁its ▁current ▁implementation , ▁old ▁versions ▁of ▁specific ▁articles , ▁images , ▁and ▁templates ▁are ▁reference able ▁by ▁unique ▁un ch anging ▁URLs , ▁though ▁current ▁entries ▁may ▁not ▁use ▁old ▁versions ▁of ▁images ▁and ▁templates . ▁ ▁P erman ent ▁links ▁to ▁specific ▁versions ▁are ▁recommended ▁for ▁cit ing ▁articles ▁from ▁sources ▁such ▁as ▁Wikipedia ▁and ▁Wik ine ws , ▁to ▁ensure ▁that ▁the ▁content ▁remains ▁un changed ▁for ▁review . ▁A ▁rev iewer ▁can ▁then ▁view ▁the ▁c ited ▁revision , ▁the ▁current ▁revision , ▁and ▁the ▁differences ▁between