Fixed JavaDoc in Hatch filters.

src/main/java/org/orekit/estimation/measurements/filtering/DualFrequencyHatchFilter.java

@@ -31,7 +31,7 @@ import org.orekit.utils.Constants;
  * temporally varying ionospheric delays. Still, the spatial variation of the ionospheric delays
  * are not compensated by this phase combination.
  * </p>
- * @see "Subirana, J. S., Hernandez-Pajares, M., & José Miguel Juan Zornoza. (2013).
+ * @see "Subirana, J. S., Hernandez-Pajares, M., and José Miguel Juan Zornoza. (2013).
  *       GNSS Data Processing: Fundamentals and Algorithms. European Space Agency.
  *       Section 4.2.3.1.1"
  *

src/main/java/org/orekit/estimation/measurements/filtering/HatchFilter.java

@@ -29,10 +29,10 @@ import org.hipparchus.util.FastMath;
  * The original Hatch filter uses a single carrier-phase measurement as a smoothing value,
  * while a divergence free combination of carrier phases can be used, as well as Doppler measurements.
  * </p>
- * @see "Subirana, J. S., Hernandez-Pajares, M., & José Miguel Juan Zornoza. (2013).
+ * @see "Subirana, J. S., Hernandez-Pajares, M., and José Miguel Juan Zornoza. (2013).
  *       GNSS Data Processing: Fundamentals and Algorithms. European Space Agency."
  *
- * @see "Zhou, Z., & Li, B. (2017). Optimal Doppler-aided smoothing strategy for GNSS navigation.
+ * @see "Zhou, Z., and Li, B. (2017). Optimal Doppler-aided smoothing strategy for GNSS navigation.
  *       GPS solutions, 21(1), 197-210."
  *
  * @author Louis Aucouturier

src/main/java/org/orekit/estimation/measurements/filtering/SingleFrequencyHatchFilter.java

@@ -30,10 +30,10 @@ import org.orekit.gnss.ObservationData;
  * pseudo-range measurement using either a Doppler measurement
  * or a carrier phase measurement.
  * </p>
- * @see "Subirana, J. S., Hernandez-Pajares, M., & José Miguel Juan Zornoza. (2013).
+ * @see "Subirana, J. S., Hernandez-Pajares, M., and José Miguel Juan Zornoza. (2013).
  *       GNSS Data Processing: Fundamentals and Algorithms. European Space Agency."
  *
- * @see "Zhou, Z., & Li, B. (2017). Optimal Doppler-aided smoothing strategy for GNSS navigation.
+ * @see "Zhou, Z., and Li, B. (2017). Optimal Doppler-aided smoothing strategy for GNSS navigation.
  *       GPS solutions, 21(1), 197-210."
  *
  * @author Louis Aucouturier