Lambeth manuscripts are included in pp. 1-8 of:
Frere, W.H. Bibliotheca musica-liturgica. A descriptive handlist of the musical and liturgical manuscripts of the middle ages..., (1894).
Researchers interested in musical manuscripts may find the Digital Image Archive of Medieval Music (DIAMM) website [1], of use.
Links:
[1] http://www.diamm.ac.uk/