+## lesson-md : convert Rmarkdown files to markdown
+lesson-md : ${RMD_DST}
+
+# Use of .NOTPARALLEL makes rule execute only once
+${RMD_DST} : ${RMD_SRC}
+ @bin/knit_lessons.sh ${RMD_SRC}
+
+## lesson-check : validate lesson Markdown.
+lesson-check : lesson-fixme
+ @bin/lesson_check.py -s . -p ${PARSER} -r _includes/links.md