+ final Matcher uc_letters_and_numbers = NHXParser.UC_LETTERS_NUMBERS_PATTERN.matcher( str );
+ if ( !uc_letters_and_numbers.matches() ) {
+ return null;
+ }
+ final Matcher numbers_only = NHXParser.NUMBERS_ONLY_PATTERN.matcher( str );
+ if ( numbers_only.matches() ) {
+ return null;
+ }
+ return str;