Listed below are works of specific relevance to the Twentieth legion, together with a select bibliography of more general works. Useful general bibliographies on the Roman Army can be found here:

Roman army bibliography by Sander van Dorst

The Roman Army: A Bibliography

Specific Studies

Esdaile, G. 1886. 'Evidence of the occupation of Bath by the XX Legion’. Som. Arch. and Nat. Hist. Soc. xxxii., 48-58.

Gervasio, M. 1910. 'Per la storia delle legioni XV Apollinaris e XX Valeria Victrix’ Saggi di storia antica…a Giulio Beloch, Roma, 353-364.

Grimes, W.F. 1930. 'Holt, Denbighshire, the works-depôt of the Twentieth Legion at Castle Lyons’. Y Cymmrodor 41.

Henig, M. 1999. 'Chester and the Art of the Twentieth Legion’ in Thacker, A. (ed.) Chester: Medieval Archaeology, Art and Architecture. 1-15.

Jarrett, M.G. 1968. 'Legio XX Valeria Victrix in Britain’. Archaeologia Cambrensis 117, 77-91.

Keppie, L. 2000. 'Legiones II Augusta, VI Victrix, IX Hispana, XX Valeria Victrix', in Le Bohec and Wolff (eds) Les Legions de Rome sous le Haut-Empire, Lyon.

Malone, S.J. 2006. Legio XX Valeria Victrix: Prosopography, archaeology and history, BAR Int Ser 1491.

Manning, W. 2000. 'The fortresses of legio XX’ in Brewer R. (ed.) Roman Fortresses and their Legions. London. 69-81.

McPake, R. 1981. 'A note on the cognomina of Legio XX', Britannia 12, 293-95.

Morgan, T. 1887. 'On the Twentieth Legion as illustrated by consular denarii', Journal of the British Archaeological Association 43, 267-74.

Mrozewicz, L. 1986. 'Legio I Italica i legio XX Valeria Victrix: zwiazki wzajemne’. Eos, LXXIV, 303-308.

Musgrave, W. with Dodwell, H. 1711. Iulii Vitalis Epitaphium, Exeter republished in Musgrave 1719 Antiquitates Britanno-Belgicae, Exeter.

Post, Rev. B. 1848. 'Historical Memoranda relating to the Twentieth Roman Legion', Transactions of the Gloucester Congress of the British Archaeological Association, 43-57.

Ritterling, E. 1925. 'Legio (XX valeria victrix)’ in Pauly-Wissowa-Kroll Real-Encyclopadie der Altertumswissenschaft XII, 1769-1781.

Rossi, R.F. 1969/70. 'Un soldato della XX legione ed un problema di cronologia tergestina', Atti dei Civici musei di storia ed arte di Trieste 6, 127-134

Swan, V.G. 1999. 'Legio XX Valeria Victrix and the Antonine Wall: new perspectives in the history of Northern Britain’ in N. Gudea (ed.) Roman Frontier Studies 1997, Proceedings of the XVIIth International Congress of Roman Frontier Studies, Oxbow Monograph 91, Oxford, 289-294.

Swan, V.G. 1999. 'The Twentieth Legion and the history of the Antonine Wall reconsidered’, Proc. Soc. Antiq. Scotland 129, 399-480.

Swan, V.G. and Philpott, R.A. 2000. 'Legio XX VV and tile production at Tarbock, Merseyside’ Britannia 31, 55-67.

Syme, R. 1934a. 'Lentulus and the origins of Moesia’ JRS 24, 113-137; Appendix 'Legio XX on the lower Danube’ 134-137.

Tomlin, R.S.O. 1992. 'The Twentieth Legion at Wroxeter and Carlisle in the First Century: The Epigraphic Evidence’. Britannia 23, 141-158.

Yébenes, S. Perea 2000. 'Hispania y la legio XX’, in Le Bohec and Wolff (eds), 581-87

General

Ritterling 1925. 'Legio' in Pauly-Wissowa-Kroll Real-Encyclopadie XII, 1211-1829.
in German and somewhat overtaken by 75 years of further discoveries – though those of us who wish to believe that the stone of C. Axonius indicates the early presence of the legion in Spain will cling to his arguments…

Le Bohec, Y. and Wolff, C. (eds) 2000. Les Légions de Rome sous le Haut-Empire collects together papers from a conference in Lyon, including many pieces on individual legions specifically seeking to update Ritterling

Parker, H.M.D. 1958 The Roman Legions. Rev. Ed.
not very revised from the 1928 version – short (very) pieces on individual legions, largely representing the picture laid out by Ritterling

Webster, Graham. 1979. The Roman Imperial Army of the first and second centuries A.D. 2nd ed.
again short pieces only on individual legions

Keppie, L. J. F. 1984. The making of the Roman army : from Republic to Empire.
very good on the late-Republican situation and the creation of the Imperial army from the proliferating legions of the opposing factions

Aquila Legionis is a Spanish (and largely Spanish language) journal devoted to legionary studies. A number of papers from earlier volumes are available for download.

I have also collected together articles from ZPE of interest to the study of the Roman legions into a handy list.

In Britain

Grimes, W.F. 1930. 'Holt, Denbighshire, the works-depôt of the Twentieth Legion at Castle Lyons'. Y Cymmrodor 41.
source of the many tile stamps (RIB 2411.76-80) and terracotta antefixes (RIB 2458.2-8) of the legion

Jarrett, M. 1968. 'Legio XX Valeria Victrix in Britain'. Archaeologia Cambrensis 117, 77-91.
40 years of work in Colchester, Gloucester, South Wales, Wroxeter, Chester, Carlisle etc. mean that this is outdated in some respects, but sound on the general picture and a good collection of (the few) sources for the later history of the legion

Manning W. 1981. Usk: The Fortress Excavations 1968-71.
background considers the military situation in the south-west in the 50s and argues for the presence of leg XX at Usk - though the precise status of the site remains a matter of some dispute

Holder, P. A. 1982. The Roman army in Britain.
excellent in its use of individuals to illustrate the general picture

Pitts, L.F. and St.Joseph, J.K. 1985. Inchtuthil.
the intended new base for legio xx, its construction and abandonment; a triumph of interpretation from limited excavation…or overly reliant on initial assumptions given the small areas actually investigated?

Hanson, W. S. 1987 Agricola and the conquest of the north.
including the role of the XXth under their old legate

Webster, G. (ed) 1988. Fortress into City.
40 years of work in Colchester, Gloucester, Wroxeter etc…try reconciling the conflicting claims for lengths of occupation at Gloucester, Usk, Wroxeter (Inchtuthil needs to fit in there somewhere too) – hours of fun for all...

Tomlin, R.S.O. 1992. 'The Twentieth Legion at Wroxeter and Carlisle in the First Century: The Epigraphic Evidence'. Britannia 23, 141-158.
good presentation of the arguments from the stone of C. Mannius Secundus re Wroxeter and report of a remarkable Carlisle document (recording the loan by Q. Cassius Secundus of 100 denarii to C. Geminius Mansuetus) and the implications of the missing v(aleria) v(ictrix)

Breeze, D.J. and Dobson, B. 1987. Hadrian's Wall, 3rd edition.
covers the role of the XXth in the construction of Hadrian's Wall (and the Antonine Wall) – but the division of responsibilities between the VIth and the XXth presented here still has some problems...hence the 4th edition, 2000.

Manning, W.H. 2000. 'The fortresses of legio XX' in Brewer, Richard J. (ed.) Roman Fortresses and their Legions

On Chester

Nash-Williams 1969. The Roman Frontier in Wales.
on Chester and the forts and Auxiliary units of the Chester command

Petch, D.F. 1987. 'The Roman Period'. Victoria County History of Cheshire Vol. I, 115-236.

Mason, D.J.P. 1988. '"Prata Legionis" in Britain', Britannia 19, 163-190 (171-180 for leg XX and Chester).
on the territorium attached the fortress, canabae etc.

Strickland, T.J. 1991. 'Third Century Chester' in King and Henig eds The Roman West in the Third Century. BAR IS 109(I), 415-444.
considering the fate of the fortress (and of the legion) in the 3rd century

Strickland, T.J. 2003.'Roman Chester'. Victoria County History of Cheshire Vol. 5

LeQuesne, C. et al. 2000. Excavations at Chester, the Roman and later defences, part 1: investigations 1978-1990.
on the construction and date of the Roman walls and their bearing on the status of Roman Chester

Mason, David J.P. 2000. Excavations at Chester, the Elliptical Building: an image of the Roman world. Excavations in 1939 and 1963-9 .

Mason, David J.P. 2001. Roman Chester: City of the Eagles.
the best recent overview of the legionary fortress

Legio XX Valeria Victrix by Steve Malone is licensed under a
Creative Commons Attribution-Non-Commercial-No Derivative Works 2.0 UK: England & Wales License.