1. On a problem of Lyndon;Baumslag, Gilbert;J. London Math. Soc.,1960
2. Sur l’équation 𝑎^{𝑀}=𝑏^{𝑁}𝑐^{𝑃}𝑑^{𝑄} dans un monoï libre;Lentin, André;C. R. Acad. Sci. Paris,1965
3. The equation 𝑎²𝑏²=𝑐² in free groups;Lyndon, R. C.;Michigan Math. J.,1959
4. The equation 𝑎^{𝑀}=𝑏^{𝑁}𝑐^{𝑃} in a free group;Lyndon, R. C.;Michigan Math. J.,1962
5. The equation 𝑎ⁿ𝑏ⁿ=𝑐ⁿ in a free group;Schenkman, Eugene;Ann. of Math. (2),1959