1. 
   PBO
   Philippine Board of Orthodontics
   Found op http://www.encyclo.co.uk/local/20895
   
   
2. 
   PbO
   Lead(II) Oxide Molar mass: 223.1994
   Found op http://www.convertunits.com/molarmass/Lead(II)+Oxide
   
   
3. 
   PBO
   Permanent Beat Officers
   Found op http://www.met.police.uk/foi/glossary.htm
   
   
4. 
   pbo
   1) Philippine board of orthodontics
   Found op http://www.mijnwoordenboek.nl/EN/crossword-dictionary/pbo/1
   
   

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