There are 2 titles associated with this firm.

@book{ wphp_965
  author={},
  year={1834},
  title={The Invalid's Hymn Book},
  publisher={John Robertson and Co.},
  address={Dublin},    }
@book{ wphp_9752
  author={},
  year={1835},
  title={The Invalid's Hymn Book},
  publisher={John Hatchard and Son [187 Piccadilly] \& Waugh and Innes [1826-1836] \& },
  address={Dublin},    }