| Materials toward a monograph of the genus Verbena. II H N Moldenke (1961) Phytologia 8: 108-152 | |
| Materials toward a monograph of the genus Verbena. VI H N Moldenke (1962) Phytologia 8: 371-384 | |
| Additional notes on the genus Bouchea. IV H N Moldenke (1974) Phytologia 29: 38-65 |