Calendar of letters, despatches, and state papers relating to the negotiations between England and Spain preserved in the archives at Simancas and elsewhere.
APA Citation
Great Britain. Public Record Office. (186219). Calendar of letters, despatches, and state papers relating to the negotiations between England and Spain preserved in the archives at Simancas and elsewhere. London: Longman, Green, Longman, & Roberts [etc.].
MLA Citation
Great Britain. Public Record Office. Calendar of Letters, Despatches, And State Papers Relating to the Negotiations Between England And Spain Preserved In the Archives At Simancas And Elsewhere. London: Longman, Green, Longman, & Roberts [etc.], 186219.
Warning: These citations may not always be complete (especially for serials).