\midheading{$W+Q$ production in combined 4FNS/5FNS, processes 421, 426}
\label{subsec:wbcombined}
These processes represent the production of a $W$ boson and one or more jets,
at least one of which is a $b$-quark, calculated by combining the 4- and 5-flavour results
of processes {\tt 401}, {\tt 411} (for {\tt 421}) and {\tt 406}, {\tt 416} (for {\tt 426}).
The selection of the final state is the same as for processes {\tt 401} and {\tt 406}, as
described in Section~\ref{subsec:wbbfilter}. The procedure for combining the two
calculations is described in refs.~\cite{Campbell:2008hh,Caola:2011pz}.