Geodesic
On almost reducible systems with almost periodic coefficients
Matematičeskie zametki, Tome 16 (1974) no. 5, pp. 789-799 
V. L. Novikov. On almost reducible systems with almost periodic coefficients. Matematičeskie zametki, Tome 16 (1974) no. 5, pp. 789-799. http://geodesic.mathdoc.fr/item/MZM_1974_16_5_a13/
@article{MZM_1974_16_5_a13,
     author = {V. L. Novikov},
     title = {On almost reducible systems with almost periodic coefficients},
     journal = {Matemati\v{c}eskie zametki},
     pages = {789--799},
     year = {1974},
     volume = {16},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1974_16_5_a13/}
}
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Voir la notice de l'article provenant de la source Math-Net.Ru

Let $\dot x=A(t)x$ be a system of two linear ordinary differential equations with almost periodic coefficients. Then there exists for any positive $\varepsilon$ an almost reducible system of equations $\dot x=B(t)x$ with almost periodic coefficients and such that $$ \sup_{-\infty<t<+\infty}\|A(t)-B(t)\|<\varepsilon. $$