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					Originally Posted by Ren Ren
					
				 
				These marks are similar to Vietnamese letters "HĐ" and "fi". 
			
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 The romanized Vietnamese alphabet has no F.    The combined letters PH are its phonetic equivalent in the written language.
(Just for additional information, there is no W  either.   OA is substituted, for instance 
oanh is pronounced something like 
wan.)