There are 2 titles associated with this firm.

@book{ wphp_11248
  author={Sandham,Elizabeth},
  year={1833},
  title={Sketches of young people, or, A visit to Brighton. By the author of The grandfather, Friendship, The schoolfellows, &c. &c.},
  publisher={Simpkin, Marshall and Co. \& Thomas Richardson \& Samuel Horsey \& Samuel Darton and Robert Harvey [1833-38] \& },
  address={London},    }
@book{ wphp_13022
  author={Brown,Eliza},
  year={1835},
  title={Children as they are; or, Tales and dialogues, for young readers from seven to twelve years of age. By the author of 'The transformation of a beech-tree.'},
  publisher={Samuel Darton and Robert Harvey [1833-38] \& Thomas Richardson \& Simpkin, Marshall and Co. \& Samuel Horsey},
  address={Derby},    }