code: public static SpaceGroup getSpaceGroup(String shortName) {
  		if (shortName==null || shortName.length()<=2) return null;
  
  		// PDB uses group "P 1-" for 13 racemic mixture entries (as of Sep2011), e.g. 3e7r
  		// they call the space group "P 1-" unusually (symop.lib and everyone else call it "P -1")
  		if (shortName.equals("P 1-")) shortName="P -1";
  
  		// enantiomorphic space groups contain sometime letters indicating glide planes which should always be lower case
  		// in some PDB entries like 4gwv they are in upper case, we fix that here: convert any non-first letter to lower case
  		shortName = shortName.substring(0, 1)+shortName.substring(1).toLowerCase();
  
  		return name2sgs.get(shortName);
  	}
docs: Get the space group for the given international short name, using
  the PDB format, e.g. 'P 21 21 21' or 'C 1 c 1'
  @param shortName
  @return the SpaceGroup or null if the shortName is not valid