SIMBAD references

We investigate a new approach to the detection of companions to extrasolar planets beyond the transit method. We discuss the possibility of the existence of ``binary planets''. We develop a method based on the imaging of a planet-companion as an unresolved system (but resolved from its parent star). It makes use of planet-companion ``mutual phenomena'', namely mutual transits and mutual shadows. We show that companions can be detected and their radius measured down to lunar sizes.