subset from a dataset after comparing its one column to a related vector

Hello R users,

I have two data sets like the following. Form of dataset:

data:

     X1       X2        X3    X4       X5
    1902       RE        3      594        9
     1903       RE        3     1340        7
     1904       AA        3      760       14
     1908       RE        4     1759       18
     1909       EX        2      387        1
     2901       AU        6     3116        2
     3801       AA        1      304       29
   3902       RE        5     2482        6

I need to select rows of a data set based on the common observations  
of X1.
Using intersect command I got the common observations of X1 from the  
two data
sets as:

common=c(1902, 1904, 1908, 1909, 3801).

Using subset command I can select portions separately. But in  
general if I am
given this type of dataset - "data" with large number of rows and  
also a list of
X1 - "common" containing many elements, can anyone please let me  
know  how to
select portion of the data whose X1 values are same as common values.

If any questions let me know.

Shant.
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