Na-montmorillonite    | 
|---|
 | USE | montmorillonite |  | SN | After 1992, use montmorillonite and sodium ion if applicable. |  
 Nan-king    | 
|---|
 | SN | Not a valid term for GeoRef. See Nanjing China. |  
 nat    | 
|---|
 
 national    | 
|---|
 
 National Aeronautics and Space Administration    | 
|---|
 | USE | NASA |  
 National Oceanic and Atmospheric Administration    | 
|---|
 | USE | NOAA |  
 National Science Foundation    | 
|---|
 | USE | NSF |  
 National Uranium Resource Evaluation Program    | 
|---|
 | USE | NURE |  
 National Water Data Exchange    | 
|---|
 | USE | NAWDEX |  
 National Water Information System-II    | 
|---|
 | USE | NWIS-II |  
 National Water-Quality Assessment Program    | 
|---|
 | USE | NAWQA |  
 native elements and alloys    | 
|---|
 | SN | As of 1981, no longer a valid term for GeoRef. Use native elements or alloys as applicable. |  
 natural    | 
|---|
 | SN | A valid index term through 1977. |  
 natural materials    | 
|---|
 | RT | materials |  |   | synthetic materials |  | SN | Used with minerals only to distinguish from synthetic materials. It is not used for natural materials which are rocks, sediments, isotopes, or commodities. Added to Thesaurus in 1968. |  
 natural selection    | 
|---|
 
 Naubug    | 
|---|
 | RT | India |  |   | Jammu and Kashmir |  |   | Pakistan |  | SN | Village SE of Srinager in S Jammu and Kashmir, disputed territory between India and Pakistan. Before 1993, India was a broader term. Indexed with Jammu and Kashmir AND India and/or Pakistan as applicable. |  
 Navajo    | 
|---|
 
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