Update README.md

README.md

@@ -55,7 +55,7 @@ Here are our definitions
 |Services_and_Facilities|This NOTAM concerns services or facilities (fuel, meteo systems (ex : AWOS, RVR systems, windsock...), rescue, wash, pushback …), but not the signs or the lights. If the NOTAM deals with this subject and does not lead to close a precise part of the aerodrome, it should be classified in this category, rather than in another one.|Why separating data (METAR) and the system which provides it (WDI)? This is to prevent to merge data & system. 
 |Signs_and_Lights|This NOTAM concerns signs or lights. If the NOTAM deals with this subject and does not lead to close a part of the aerodrome, it should be classified in this category, rather than in another one.| 
 |Taxiway|This NOTAM concerns taxiway state or taxilane state (closure, degraded surface, work in progress around taxiway). Taxiway signs and lights are NOT part of this category, except if the consequence is one of the above cases.| 
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+|Terminal_or_Enroute_Navaids|   This NOTAM concerns terminal or enroute navaids (VOR, DME, NDB, ADF...), mainly used for position computation||
 
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