by no means clear that all the singularities (for instance the strong curvature shell-focusings) have counterparts in flat spacetime evolution. At the very least, this has to be investigated further, so as to get a precise distinction of the singularities that have Minkowskian analogs, from those that are of purely relativistic origin.

It is however more useful to examine cosmic censorship keeping the astrophysical context in mind, and here we know that a fluid description of stellar matter is physically quite appropriate. Thus, if a naked singularity were to result in the collapse of a real star made of fluid matter, we would be compelled to seriously pursue its observational consequences.

Collapse of a Massless Scalar Field
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In a series of papers, Christodoulou [@ch] has pioneered analytical studies of the spherical collapse of a self-gravitating massless scalar field. He established the global existence and uniqueness of solutions for the collapsing field, and also gave sufficient conditions for the formation of a trapped surface. For a self-similar scalar collapse he showed that there are initial conditions which result in the formation of naked singularities.

Christodoulou was also interested in the question of the mass of the black hole which might 