Statistics on keywords

It may be useful to know how many references containing one, two or three keywords can be expected in one year. A command bib like

bib -w year keyword_1 [keyword_2 keyword_3]

displays the number of references for the given year which contains the listed keywords.

It works for only one year at a time. The year should be indicated by the last two digits.

Example:

bib -w 92 Hyades lithium

will give an answer like:

" Keywords (1992) : Hyades lithium : 3 references"