@article{piaggio_1913, 
  title={Some Non-Primary Perpetuant Syzygies of the Second Kind}, 
  volume={s2-12}, 
  DOI={10.1112/plms/s2-12.1.377}, 
  publisher={Oxford University Press (OUP)}, 
  author={Piaggio}, 
  year={1913}
  }