Extending makefile to pdf and html output

[Heime]

I want to add the production of pdf and html.  How would one
change this makefile?

btnver = hist-1.0
prxdir = ${HOME}/Opfeld/hist/1-devel
srcdir = ${prxdir}/${btnver}/orellana/skemaru/antares

trgdir = ${HOME}/Opfeld/hist/installs/${btnver}

MAKEINFO = makeinfo
MAKEINFOFLAGS = --no-split

.PHONY: info

info: $(trgdir)/antares.info

$(trgdir)/%.info: $(srcdir)/%.texi
        ## Make any missing parent directories
        mkdir -p $(trgdir)
        $(MAKEINFO) $(MAKEINFOFLAGS) -o $@ $<

clean:
        rm -f ${trgdir}/antares.info