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 <p><h4 id="pppar">2.13.2.10 PPP-AR Options - optional</h4></p>
 <p>
-The algorithm for the ambiguity resolution is the Best Integer Equivariant (BIE) algorithm.
-The BIE algorithm is described in <p> Teunissen, P. J. G., "GNSS Best Integer Equivariant Estimation."
-In A Window on the Future of Geodesy Sanso, F., Berlin: Springer. Inpress.</p>
-and generally reveals float ambiguities, not integers. However, the distance between the (float) BIE
+The algorithm for the ambiguity resolution is the Best Integer Equivariant (BIE) algorithm described in Teunissen (2005).
+It generally reveals float ambiguities, not integers. However, the distance between the (float) BIE
 result and the nearest integer (the fractional part of the BIE result) is a very good criterion for the reliability of the resolved ambiguity.
 In addition it is possible to compute a variance (or its squareroot – sigma) of each resulting BIE ambiguity.
 </p>
+<p>
+Reference:
+</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.
+<a href="https://doi.org/10.1007/3-540-27432-4_72" target="_blank">https://doi.org/10.1007/3-540-27432-4_72</a>
+</p>
+
 <p><h4 id="ppparsys">2.13.2.10.1 Constellations - optional</h4></p>
 <p>