A differential method of search for the CMBR spectral-spatial   fluctuations
  The CMBR spectral-spatial fluctuations (SSF) formed in early Universe during the Dark Ages are considered. Main attention is focused on the narrow-band spectral properties of the SSF. Based on these properties we propose to use a differential method in order to search for these fluctuations. Description of the method is given. 
V.K. Dubrovich, A.T. Bajkova