Correlation between background events detected on 23 February 1987 by the LSD apparatus and the Baksan telescope
Alekseev E. N., Alekseeva L. N., Zakidyshev V. N., Klimenko N. F. , Kogai I. M., Krivosheina I. V. , Poddubnyi V. A.
A joint analysis of the data recorded over the time interval 1:45-3:45 UT on 23 February 1987 by the LSD apparatus and the Baksan telescope reveals a correlation between natural radioactivity and high-energy cosmic-ray muons.