Index: trunk/BNC/src/bnchelp.html
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   <li>the <b>BIE</b> (Best Integer Equivariant) weighting for the final estimate.</li>
 </ul>
-The Best Integer Equivariant (BIE) algorithm is described in 
+References:
+</p>
+<p>
+Teunissen P.J.G. (1993) Least-squares estimation of the integer GPS ambiguities, Invited Lecture, Section IV Theory and Methodology, 
+IAG General Meeting, Beijing, China, August 1993. Also in: LGR Series, No. 6, Delft Geodetic Computing Centre.
+<a href="https://gnss.curtin.edu.au/wp-content/uploads/sites/21/2016/04/Teunissen1993Least.pdf" target="_blank">https://gnss.curtin.edu.au/wp-content/uploads/sites/21/2016/04/Teunissen1993Least.pdf</a>
+
+</p>
 <p>
 Teunissen P.J.G. (2005) GNSS Best Integer Equivariant Estimation. In book: A Window on the Future of Geodesy. pp. 422-427. Sanso, F., Berlin: Springer. Inpress.