e^+e^- annihilation data recorded by the JADE detector at PETRA were used to measure the C-parameter for the first time at sqrt{s}= 35 and 44 GeV. The distributions were compared to a resummed QCD calculation. In addition, we applied extended resummed calculations to the total and wide jet broadening variables, B_T and B_W. We combined the results on alpha_s with those of our previous study of differential 2-jet rate, thrust, and heavy jet mass, obtaining alpha_s(35 GeV) = 0.1448 +0.0117 -0.0070 and alpha_s(44 GeV) = 0.1392 +0.0105 -0.0074. Moreover power corrections to the mean values of the observables mentioned above were investigated considering the Milan factor and the improved prediction for the jet broadening observables. Our study, which considered e^+e^- data of five event shape observables between sqrt{s}= 14 and 183 GeV, yielded alpha_s(M_{Z^0})=0.1177 +0.0035 -0.0034.
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