@article{leinert_1976, 
  title={A commutative Banach algebra which factorizes but has no approximate units}, 
  volume={55}, 
  DOI={10.1090/s0002-9939-1976-0397312-3}, 
  publisher={American Mathematical Society (AMS)}, 
  author={Leinert}, 
  year={1976}, 
  month={Feb}
  }