Strong Gravitational Lensing and Localization of Merging Massive Black Hole Binaries with LISA

We study how the angular resolution of LISA for merging massive black-hole binaries would be improved if we observe multiple gravitational wave ``images'' due to strong gravitational lensing. The correlation between fitting parameters is reduced by the additional information of the second image which significantly reduces the error box on the sky. This improvement would be very helpful for identifying the host galaxy of a binary. The angular resolution expected with multiple detectors is also discussed.