Abstract
The review is withdrawn as it has not been maintained since its first publication in 2001 (searches date back to the year 2000). Since then, new trials have been published that may or may not change the conclusions of the review. A new team of authors overtook the review on 26.10.2020, and the new review is expected to be published by the beginning of 2022. The review will be prepared based on most recent Cochrane methods. Readers may still find the outdated review on the CDSR (the Cochrane Library).