TY - GEN AU - W A Horn C2 - , National Institute of Standards and Technology, Gaithersburg, MD DA - 1971-01-01 05:01:00 DO - https://doi.org/10.6028/NBS.RPT.10500 LA - en PB - , National Institute of Standards and Technology, Gaithersburg, MD PY - 1971 TI - Some recent theoretical work on accessibility in transportation systems: ER -