The tangent space in sub-Riemannian geometry.- 1. Sub-Riemannian manifolds.- 2. Accessibility.- 3. Two examples.- 4. Privileged coordinates.- 5. The tangent nilpotent Lie algebra and the algebraic structure of the tangent space.- 6. Gromov's notion of tangent space.- 7. Distance estimates and the metric tangent space.- 8. Why is the tangent space a group?.- References.- Carnot-Carathéodory spaces seen from within.- 0. Basic definitions, examples and problems.- 1. Horizontal curves and small C-C balls.- 2. Hypersurfaces in C-C spaces.- 3. Carnot-Carathéodory geometry of contact manifolds.- 4. Pfaffian geometry in the internal light.- 5. Anisotropic connections.- References.- Survey of singular geodesics.- 1. Introduction.- 2. The example and its properties.- 3. Some open questions.- 4. Note in proof.- References.- A cornucopia of four-dimensional abnormal sub-Riemannian minimizers.- 1. Introduction.- 2. Sub-Riemannian manifolds and abnormal extremals.- 3. Abnormal extremals in dimension 4.- 4. Optimality.- 5. An optimality lemma.- 6. End of the proof.- 7. Strict abnormality.- 8. Conclusion.- References.- Stabilization of controllable systems.- 0. Introduction.- 1. Local controllability.- 2. Sufficient conditions for local stabilizability of locally controllable systems by means of stationary feedback laws.- 3. Necessary conditions for local stabilizability by means of stationary feedback laws.- 4. Stabilization by means of time-varying feedback laws.- 5. Return method and controllability.- References.
