pfSense-On-A-Stick - 802.1Q Trunking With pfSense 2.0 RC1 and Mikrotik RouterBoard RB250G Smart Gigabit Switch with five ports and SwOS v1.5 - Stefcho's Tech Blog
Netgate 1100 Security Gateway Manual — Configuring a Router on a Stick | Netgate Documentation
Inter-vlan routing using router on stick - IT Funkaar
Making pfSense router on a stick (This actually works) : r/PFSENSE