| title = Chicago Wilderness Journal, Volume 1 - Number 1 - November, 2003 | url = http://www.chicagowilderness.org/pubprod/cwjournal/docs/CWJournal1003.pdf
}}</ref>
[[en:'''Density gradient''' is a spatial variation in [[density]] over an area. The term is used in the [[natural sciences]] to describe varying density of [[مادة]], but can apply to any [[quantity]] whose density can be [[measured]].<ref>{{cite web
| title = Non-Destructive Testing Resource Center - Glossary | url = http://www.ndt-ed.org/GeneralResources/Glossary/letter/d.htm
}}</ref>
<ref>{{cite web
| title = Chicago Wilderness Journal, Volume 1 - Number 1 - November, 2003 | url = http://www.chicagowilderness.org/pubprod/cwjournal/docs/CWJournal1003.pdf
