Select common rows from two different arrays

I have 161 different csv files, each csv file has about 20000 rows and 4 columns. I want to select the rows which have common first column elements and save them in a new array. Please help me how to progress with this problem.

[Sven]

Do they need to be common to *all* 161 of your different files, or do you just want *any* row that exists in at least two of your files?

[Sven]

Please make a very small example that shows what you want done. For example:

file1 = [1 3; 2 4; 3 3; 10 4];

file2 = [1 5; 1 6; 4 4; 12 5; 16 1];

file3 = [1 4; 10 4; 16 3];

If this was the contents of your file, what would you want your output to be?