  The projected multiplicity function of galaxies gives (per square degree) the
density of galaxy aggregates formed by N members. We use the CRoNaRio matched
catalogues to derive the low N (N<15) multiplicity function from D-POSS data.
The van Albada (1982) algorithm was implemented and used to identify candidate
groups in the CRoNaRio catalogues. In absence of redshift surveys complete down
to the magnitude limit of the DPOSS material and covering a wide enough area,
the performances of the algorithm were tested on realistically simulated
catalogues. The application to a set of 13 CRoNaRio catalogues allowed us to
derive a multiplicity function as accurate as those available in literature
obtained from redshift surveys.
