R(s) and hadronic tau-Decays in Order alpha_s^4: technical aspects

Understand

We report on some technical aspects of our calculation of alpha_s^4 corrections to R(s) and the semi-leptonic tau decay width [1-3].

• We discuss the inner structure of the result as well as the issue of its correctness.
• We demonstrate recently appeared independent evidence positively testing one of two components of the full result.