Normal frames and the validity of the equivalence principle. I. Cases in   a neighborhood and at a point
  A treatment in a neighborhood and at a point of the equivalence principle on the basis of derivations of the tensor algebra over a manifold is given. Necessary and sufficient conditions are given for the existence of local bases, called normal frames, in which the components of derivations vanish in a neighborhood or at a point. These frames (bases), if any, are explicitly described and the problem of their holonomicity is considered. In particular, the obtained results concern symmetric as well as nonsymmetric linear connections. 
Bozhidar Z. Iliev (Inst. Nucl. Res. & Nucl. Energy, Sofia, Bulgaria)