• Piers Plowman Electronic Archive, by William Langland (HTML at ncsu.edu). Currently focuses primarily on B-Text manuscripts.
• The Vision of William Concerning Piers Plowman (4 volumes in 5, EETS original series 28, 38, 54, 67, and 81; London: Pub. for the Early English Text Society by N. Trubner and Co., 1867-1885), by William Langland, ed. by Walter W. Skeat
  • Volume I (Text A): multiple formats at Google
  • Volume II (Text B): multiple formats at Google
  • Volume III (Text C): multiple formats at Google
  • Volume IV Section I (Notes to Texts A, B, and C): multiple formats at Google
  • Volume IV Section II (General preface, notes, and indexes): multiple formats at Google
  Includes texts and notes for all 3 major versions.
• The Vision of William Concerning Piers the Plowman, in Three Parallel Texts; Together With Richard the Redeless (2 volumes; Oxford: At the Clarendon Press, 1886), by William Langland, ed. by Walter W. Skeat (page images at HathiTrust)

These editions present one text of the poem, possibly derived from multiple manuscripts or versions.

• William Langland's The Vision of Piers Plowman (main text from the 1978 Dent and Dutton edition), by William Langland (HTML at Michigan)
• The Vision of William Concerning Piers the Plowman, by William Langland (or Langley), According to the Version Revised and Enlarged by the Author, About A.D. 1377 (ninth edition; Oxford: At the Clarendon Press, 1906), by William Langland, ed. by Walter W. Skeat (multiple formats at archive.org)

• Look for editions of this book at your library, or elsewhere.