Soundex is one technique for indexing names such that phonetic equivalents, with variations in transliterations into the local language, can be retrieved.
19.
These encoding rules are available from NARA, upon request, in the form of General Information Leaflet 55, " Using the Census Soundex ".
20.
It takes constant time to calculate soundex ( just replace the letters with numbers ) and then constant time to lookup the soundex code in a table.