A method and an apparatus for demodulating a downlink control channel by a relay node in a wireless communication system. Apparatus and methods are provided for calibrating an electronic book system including temperature compensation steps. It is obtained by inhibiting the most immunogenic part of the bioaragonite organic substance so as to maintain bioactive only the organic part associated with the mineral capable of having a positive effect. The cage includes substantially spherical inner and outer surfaces which engage the land surfaces on the inner and outer joint parts respectively.