Infinite highly arc transitive digraphs and universal covering digraphs

@article{Cameron1993InfiniteHA,
  title={Infinite highly arc transitive digraphs and universal covering digraphs},
  author={Peter J. Cameron and Cheryl E. Praeger and Nicholas C. Wormald},
  journal={Combinatorica},
  year={1993},
  volume={13},
  pages={377-396}
}