@article{robbertse_westhuizen_vorster_1989, 
  title={Encephalartos middelburgensis (Zamiaceae): a new species from the Transvaal}, 
  volume={55}, 
  DOI={10.1016/s0254-6299(16)31240-6}, 
  publisher={Elsevier BV}, 
  author={Robbertse and Westhuizen and Vorster}, 
  year={1989}
  }