	Hermenegildo Arruga i Liró	Arruga's Suture	Arruga Needle Holder	Arruga Forceps	Michele Arslan
Art Gallery Theorem	Artin Approximation Theorem	Arthur Russel	Arthurite	Arthur Kingsbury	King Arthur
Emil Artin	Artin Reciprocity Law	José Gervasio Artigas	Artiguism	$Artstein's Circles is a theorem which states that a nonlinear dynamical system in the control-affine form which has a differentiable control-Lyapunov function if and only if it admits a regular stabilizing feedback u(x), that is a locally Lipschitz function on Rn\{0}. The original proof of Zvi Artstein proceeds by a nonconstructive argument. In 1989 Eduardo D. Sontag provided a constructive version of this theorem explicitly exhibiting the feedback.$ Artstein's Circles	Zvi Artstein
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