Bibtex errors and warnings

/tmp/irad.bib, line 1, warning: overriding existing definition of macro "jcp"
/tmp/irad.bib, line 2, warning: overriding existing definition of macro "sisc"
/tmp/irad.bib, line 3, warning: overriding existing definition of macro "sissc"
/tmp/irad.bib, line 4, warning: overriding existing definition of macro "sinum"
/tmp/irad.bib, line 5, warning: overriding existing definition of macro "gafd"
/tmp/irad.bib, line 6, warning: overriding existing definition of macro "jsc"