  We introduce an approach to automatic indexing of e-prints based on a
pattern-matching technique making extensive use of an Associative Patterns
Dictionary (APD), developed by us. Entries in the APD consist of natural
language phrases with the same semantic interpretation as a set of keywords
from a controlled vocabulary. The method also allows to recognize within
e-prints formulae written in TeX notations that might also appear as keywords.
We present an automatic indexing system, AUTEX, which we have applied to
keyword index e-prints in selected areas in high energy physics (HEP) making
use of the DESY-HEPI thesaurus as a controlled vocabulary.
