refs

- Kuwata, Wolf, Zarzhitsky, Huntsberger (2014) "Safe Maritime Autonomous
  Navigation With COLREGS, Using Velocity Obstacles", IEEE JOE 39(1):110-119.
  THE paper for our avoidance layer.
- "Formal Verification of Path Planning Safety and Reachability in USVs"
  (Springer LNCS, 2024). use for the cert argument (reachability props).