The sixth seeds beat Jonathan Erlich and M Kohlmann 3-6 6-1 10-5 in one hour and nine minutes in the second round of the euro 2,750,000 ATP event.
They will next face second seeds Daniel Nestor of Canada and Nenad Zimonjic of Serbia. Leander Paes and Lukas Dlouhy, who have already qualified for the season-ending finale in London, are also in the quarter-finals.
Rohan Bopanna and Aisam-ul-haq Qureshi are also striving to qualify for the World Tour finals.
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