Complex sentence: During these years, Rossetti was prevailed upon by friends, in particular Charles Augustus Howell, to exhume his poems from his wife's grave which he did, collating and publishing them in 1870 in the volume "Poems by D. G. Rossetti".
Split into simpler sentences: During these years, Rossetti was prevailed upon by friends, in particular Charles Augustus Howell, to exhume his poems from his wife's grave. This he did, collating and publishing them in 1870 in the volume "Poems by D. G. Rossetti".