MathSciDoc: An Archive for Mathematician ∫

@inproceedings{j.1965extensions,
  title={Extensions in varieties of groups and algebras},
  author={J. Knopfmacher},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203207648542003},
  booktitle={Acta Mathematica},
  volume={115},
  number={1},
  pages={17-50},
  year={1965},
}