Sources

General introduction to Milnor invariants:

• [Meilhan] Linking number and Milnor invariants - preliminary chapter for the upcoming Concise Encyclopedia of Knot theory
• [Gadgil] Watson-Crick pairing, the Heisenberg group and Milnor invariants

Original sources:

• [Milnor] Link Groups
• [Milnor] Isotopy of links - appears in [Fox, Algebraic Geometry and Topology: A Symposium in Honor of Solomon Lefschetz]
• [Chen] Isotopy Invariants of Links

Link homotopy:

• [Habegger, Lin] The Classification of Links up to Link-Homotopy

Connection between Milnor invariants and Massey products

• [Porter] Milnor's invariants and Massey products
• [Turaev] Milnor invariants and Massey products
• [Cochran] Derivatives of links: Massey products and Milnor’s concordance invariants - this contains a process for taking any desired Massey product and realizing it as the Massey product of a link

Milnor invariants from surfaces:

• [Mellor, Melvin] A geometric interpretation of Milnor's triple linking numbers - mu-bar_{ijk} from intersections of Seifert surfaces
• [Davis, Nagel, Orson, Powell] Triple linking numbers and surface systems

Concordance:

• [Stallings] Homology and central series of groups - The remark on I-equivalence yields the concordance invariance of the Milnor invariants
• [Casson] Link Cobordism and Milnor's Invariant
• [Giffen] Link Concordance implies Link Homotopy
• [Meilhan, Yasuhara] Link concordances as surfaces in 4-space (arXiv:1910.06214)

Conant, Schneiderman and Teichner:

• [Conant, Schneiderman, Teichner] Higher Order Intersections in Low-Dimensional Topology - Survey article
• [Conant, Schneiderman, Teichner] Whitney tower concordance of classical links - Introduction to Whitney towers
• [Conant, Schneiderman, Teichner] Milnor Invariants and Twisted Whitney Towers
• [Conant, Schneiderman, Teichner] Cochran's βi invariants via twisted Whitney towers

Finite type invariants:

• [Bar-Natan] Vassiliev homotopy string link invariants - showed that any Milnor string link invariant of length k is a finite type invariant of degree k−1
• [Lin] Power Series Expansions And Invariants Of Links
• [Habegger, Masbaum] The Kontsevich integral and Milnor’s invariants - Milnor string link invariants can be extracted from the Kontsevich integral, which is universal among finite type invariants
• [Komendarczyk, Michaelides] Tree invariants and Milnor linking numbers with indeterminacy

Arithmetic Topology:

• [Morishita] Milnor invariants and Massey products for prime numbers
• [Baez] This Week's Finds in Mathematical Physics (Week 257)

Other:

• [Nick Salter] Massey products, the lower central series, and the Poincare conjecture - Handwritten notes from a talk on Massey products
• [DeTurck, Gluck, Komendarczyk, Melvin, Shonkwiler, Vela-Vick] Triple linking numbers, ambiguous Hopf invariants and integral formulas for three-component links