Bibtex errors and warnings

/tmp/orna.bib, line 1, warning: overriding existing definition of macro "jan"
/tmp/orna.bib, line 2, warning: overriding existing definition of macro "feb"
/tmp/orna.bib, line 3, warning: overriding existing definition of macro "mar"
/tmp/orna.bib, line 4, warning: overriding existing definition of macro "apr"
/tmp/orna.bib, line 5, warning: overriding existing definition of macro "may"
/tmp/orna.bib, line 6, warning: overriding existing definition of macro "jun"
/tmp/orna.bib, line 7, warning: overriding existing definition of macro "jul"
/tmp/orna.bib, line 8, warning: overriding existing definition of macro "aug"
/tmp/orna.bib, line 9, warning: overriding existing definition of macro "sep"
/tmp/orna.bib, line 10, warning: overriding existing definition of macro "oct"
/tmp/orna.bib, line 11, warning: overriding existing definition of macro "nov"
/tmp/orna.bib, line 12, warning: overriding existing definition of macro "dec"
/tmp/orna.bib, line 17, warning: overriding existing definition of macro "jcss"
/tmp/orna.bib, line 26, warning: overriding existing definition of macro "pnas"
/tmp/orna.bib, line 34, warning: 1 characters of junk seen at toplevel
invalid token near line 38 (text was ''')
/tmp/orna.bib, line 38, syntax error: found "ppolito", expected "="
/tmp/orna.bib, line 38, syntax error: found "=", expected end of entry ("}" or ")") (skipping to next "@")
/tmp/orna.bib, line 39, warning: 37 characters of junk seen at toplevel
invalid token near line 60 (text was ''')
/tmp/orna.bib, line 60, syntax error: found "r", expected "="
/tmp/orna.bib, line 60, syntax error: found "=", expected end of entry ("}" or ")") (skipping to next "@")
/tmp/orna.bib, line 61, warning: 20 characters of junk seen at toplevel