1. 
   H2
   acronym: hydrogen
   Found op http://cdiac.ornl.gov/pns/acronyms.html#H
   
   
2. 
   h2
   The ratio between genetic variance and phenotypic variance used by plant breeders in selecting for yield, resistance or other characteristics.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
3. 
   H2
   Header 2 / Second half of the year, details ...
   Found op http://www.cryer.co.uk/glossary/h/index.htm
   
   
4. 
   H2
   Hydrogen.
   Found op http://www.youngco.com/young2.asp?ID=4&Type=3
   
   

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