Sexual Powers Hadith

I have read a hadith somewhere which says something like > Anas bin Malik said, "The Prophet used to visit all his wives in a > round, during the day and night and they were eleven in number." I > asked Anas, "Had the Prophet the strength for it?" Anas replied, "We > used to say that the Prophet was given the strength of thirty (men)." > And Sa`id said on the authority of Qatada that Anas had told him about > nine wives only (not eleven) Is this hadith authentic?