@article{DeneckeKoppitzŠtrakov2006,
  author    = {Klaus-Dieter Denecke and J{\"o}rg Koppitz and Slavčo Štrakov},
  title     = {Multi-hypersubstitutions and colored solid varieties},
  journal   = {International journal of algebra and computation},
  volume    = {16},
  number    = {4},
  pages     = {797 -- 815},
  doi       = {10.1142/S0218196706003189},
  year      = {2006},
}