AUTHOR=Ha Hyun-Joon TITLE=Editorial: Strained Aza-Heterocycles in Synthesis JOURNAL=Frontiers in Chemistry VOLUME=7 YEAR=2019 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00669 DOI=10.3389/fchem.2019.00669 ISSN=2296-2646