Get or create bibstyle JSSextra or clones of it for derived bib styles.
bibstyle_JSSextra(style = "JSSextra", reset = FALSE, make_default = FALSE)an environment
the name of the style. The default is "JSSextra".
if TRUE, create a fresh copy of the style even if it exists.
if TRUE, make the style default.
Georgi N. Boshnakov
bibstyle_JSSextra() returns the bib style "JSSextra"
(i.e., its environment, not the name of the style). If
"JSSextra" has not been created yet, it creates it first.
If argument style is used, as in
bibstyle_JSSextra("mystyle"), a style "mystyle" initially
equivalent to "JSSextra" is returned (it is created if
necessary). The returned environment can be amended to derive a new
bib style.