'Correspondence of Scientific Men of the Seventeenth Century: Including Letters of Barrow, Flamstead, Wallis, and Newton, Printed from the Originals in the Collection of the Right Honourable the Earl of Macclesfield', S.P. Rigaud, 2 vols (Oxford, 1841.) At lower levels this is abbreviated to 'Rigaud'; 'The Correspondence of Isaac Newton', ed. H.W. Turnbull, 7 vols (Cambridge, 1959-1977.) At lower levels this is abbreviated to 'Corr'; 'The Mathematical Papers of Isaac Newton', ed. D. Whiteside, 8 vols (Cambridge, 1967-1981.) At lower levels this is abbreviated to 'MP'.