anchor.diff:  Open Post Codes have an optional checksum that can be used to distinguish
   the country a code was generated for.
   
  -== link:http://nacgeo.com[Natural Area Code]
  -
  -Natural Area Code is a proprietary system that requires licenses to use
  +== Natural Area Code
  +
  +Natural Area Code <<nac-site>> is a proprietary system that requires licenses to use
   <<naclicense>>. The codes are made up of up to three parts, the first
   provides the latitude, the second the longitude and an optional third part
   the altitude as the arctangent of the altitude relative to the Earth's
  
positive.code: 
  - [[[openpostcode]]] In Wikipedia. Retrieved October 15 2014 from http://en.wikipedia.org/wiki/Postal_addresses_in_the_Republic_of_Ireland
  
  - [[[naclicense]]] Legal and Licensing Retrieved October 15 2014 from http://www.nacgeo.com/nacsite/licensing/
  
  - [[[nac]]] The Natural Area Coding System Retrieved October 15 2014 from http://www.nacgeo.com/nacsite/documents/nac.asp
  
  - [[[mls]]] In Wikipedia. Retrieved October 15 2014 from http://en.wikipedia.org/wiki/Maidenhead_Locator_System
  
negative.code: locations. We think that this shows latitude and longitude have too many
  disadvantages to be adopted for a street addressing solution.
  
  == Geohash
  
  Geohash codes <<geohash-site>> were designed to be used in short URLs to identify locations
  <<geohash32>>. They use 32 characters in their symbol set made up of 0-9A-Z excluding
  "A", "I", "L" and "O". This means that Geohash codes can include vowels (and
  the digits "0" and "1" with a similar appearance to "0" and "I"). Geohash
  can generate codes that include words ("DRUGGED"), almost words ("ZUR1CH")
  