Dan, Meyer. "Growing Wisconsin Trees From Seed"(PDF). University of Wisconsin College of Agricultural and Life Sciences. Archived from the original(PDF) on 10 Sep 2016. Retrieved 2008-07-01.
"Growing Milkweed". University of Minnesota Monarch Lab. Archived from the original on 17 November 2014. Retrieved 4 November 2022.
wisc.edu
forest.wisc.edu
Dan, Meyer. "Growing Wisconsin Trees From Seed"(PDF). University of Wisconsin College of Agricultural and Life Sciences. Archived from the original(PDF) on 10 Sep 2016. Retrieved 2008-07-01.