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Here you can find the dates for Wagner's Die Walküre with Karita as Sieglinde at Houston Grand Opera: https://www.houstongrandopera.org/Site/tickets/calendar/view.aspx?PerfId=2603
Here you can find the dates for Karita's 'Ah, perfido!' by Beethoven with the San Francisco Symphony: http://www.sfsymphony.org/Buy-Tickets/2014-2015/Beethovens-Pastoral-Symphony.aspx