There are 2 titles associated with this firm.

@book{ wphp_15364
  author={Richardson,Caroline E.},
  year={1828},
  title={Poems. By Mrs. G. G. Richardson, Dumfries.},
  publisher={Robert Cadell and Co. [41 St. Andrew Street] \& Simpkin, Marshall and Co. \& John Sinclair},
  address={Edinburgh},    }
@book{ wphp_12406
  author={Richardson,Caroline E.},
  year={1829},
  title={Poems. By Mrs. G. G. Richardson, Dumfries.},
  publisher={Robert Cadell and Co. [41 St. Andrew Street] \& Simpkin, Marshall and Co. \& John Sinclair},
  address={Edinburgh},    }