Recursively Presented Two Generated Infinite p-Groups. Narain Gupta (1984/1985) Mathematische Zeitschrift
Reduced Forms for Quadratic Words and Spines of 2-manifolds. E.C. Turner, R.Z. Goldstein (1981) Mathematische Zeitschrift
Regular geodesic languages and the falsification by fellow traveler property. Elder, Murray (2005) Algebraic & Geometric Topology
Representation of Markoff's binary quadratic forms by geodesics on a perforated torus Harvey Cohn (1971) Acta Arithmetica
Rescuing the Whitehead Method for Free Products, I: Peak Reduction. Donald J. Collins, Zieschang Heiner (1984) Mathematische Zeitschrift
Rescuing the Whitehead Method for Free Products, II: The Algorithm. Heiner Zieschang, Donald J. Collins (1984) Mathematische Zeitschrift