A character string of  length eight to twelve characters.  (For purposes of
this description  characters are ordered from left to right --  "first" means
"leftmost".)
The rightmost eight characters are always digits. 
If the length is 9, then the first character must be alphabetic.
If the length is 10, then the first two characters must be either both digits
or both aplhabetic.
If the length is 11,  then the first character must be alphabetic, the next
two characters must be either both digits or both alphabetic.
If the length is 12,  then the first two characters must be alphabetic and the
remaining characters digits.

An LCCN is to be normalized to its canonical form described in the syntax
description above, as follows:
1. Remove all blanks.
2. If there is a forward slash (/) in the string, remove it, and remove all
   characters to the right of the forward slash.
3. If there is a hyphen in the string:
     a. Remove it.
     b. Inspect the substring following (to the right of) the (removed) hyphen.
        Then (and assuming that steps 1 and 2 have been carried out):
           i.  All these characters should be digits, and there should be six
               or less.
           ii. If the length of the substring is less than 6, left-fill the
               substring with zeros until  the length is six.

Examples:
     "n78-890351" normalizes to "n78890351".  
     "n78-89035" normalizes to "n78089035".  
     "n  78890351 " normalizes to  "n78890351".  
     "   85000002 "  normalizes to  "85000002" 
     "85-2 "  normalizes to  "85000002" 
     "2001-000002" normalizes to  "2001000002" 
     "75-425165//r75" normalizes to "75425165"      
     "   79139101 /AC/r932" normalizes to "79139101"

The LCCN namespace consists of identifiers, one corresponding to every
assigned LCCN (Library of Congress Control Number). Any LCCN may have various
forms which all normalize to a single canonical form; only normalized values
are included in the LCCN namespace.	
	An LCCN is an identifier assigned by the Library of Congress for a
metadata record (e.g., bibliographic record, authority record). LCCNs have
three components: prefix, year, and serial number. The prefix is optional; if
present, it has one to three lowercase alphabetic characters. (Prefixes are
maintained in a controlled list.) The year is two or four digits. (For 2000 and
earlier the year is two digits, for 2001 and later, four digits.) The serial
number (after normalization) is six digits. (An un-normalized LCCN may have a
serial number of 1-6 digits, which is left-filled with zeros when normalized.)