Intersection of two datatype files

To answer the question "Which are the clusters that have at the same time data in the UBV and RIC photometric systems?" one should use the command slm and the option -int . One has to indicate also which are the data types of interest, with a syntax like:

slm "data type 1" -int "data type 2"

If a cluster catalogue designation is added, ngc, ic or anon, the intersection will be restricted to this catalogue.

The next item describes a conditional intersection.

Examples:

slm ubv -int ric: answers to the above question
slm gk -int ddo: lists clusters that have red giants and observations in the DDO photometric system
slm gk -int ddo ngc: does the same job, but limits the selection to NGC clusters