Variations of cosmic rays muon intensity in the declining phase of the   23rd solar cycle in ground and shallow underground data
  The cosmic-ray intensity record from Belgrade muon detectors in the period 2002-2004 is subjected to power spectra analysis. Statistically significant peaks are found in datasets from both ground and underground (25 m w.e.) detectors. The possible origin of these periodicities is discussed. 
Aleksandar Dragi\'c, Radomir Banjanac, Vladimir Udovi\v{c}i\'c, Dejan   Jokovi\'c, Jovan Puzovi\'c and Ivan Ani\v{c}in
astro-ph.SR astro-ph.IM