1. One-variable equations in free groups;Appel, K. I.;Proc. Amer. Math. Soc.,1968
2. Solution of systems of equations in one unknown in free groups;Lorenc, A. A.;Dokl. Akad. Nauk SSSR,1963
3. Equations in free groups;Lyndon, Roger C.;Trans. Amer. Math. Soc.,1960
4. Groups with parametric exponents;Lyndon, Roger C.;Trans. Amer. Math. Soc.,1960
5. The equation 𝑎^{𝑀}=𝑏^{𝑁}𝑐^{𝑃} in a free group;Lyndon, R. C.;Michigan Math. J.,1962