+## lesson-md : convert Rmarkdown files to markdown
+lesson-md : ${RMD_DST}
+
+_episodes/%.md: _episodes_rmd/%.Rmd
+ @bin/knit_lessons.sh $< $@
+
+## lesson-check : validate lesson Markdown.
+lesson-check : lesson-fixme
+ ${PYTHON} bin/lesson_check.py -s . -p ${PARSER} -r _includes/links.md