In the physical literature about the n -body problem (n ≥ 3), sometimes reference is made to "the impossibility of solving the n -body problem" (via employing the above approach). However, care must be taken when discussing the 'impossibility' of a solution, as this refers only to the method of first integrals (compare the theorems by Abel and Galois about the impossibility of solving algebraic equations of degree five or higher by means of formulas only involving roots).