Akiyama, K., Ogawa, M. and Suetake, C. 2009. On ${\rm STD}_6[18,3]$’s and ${\rm STD}_7[21,3]$’s Admitting a Semiregular Automorphism Group of Order 9. The Electronic Journal of Combinatorics. 16, 1 (Dec. 2009), R148. DOI:https://doi.org/10.37236/237.