Z3950 returning two records?

I have this simple scripts that looks up ISSN and returns the subject. Why it is returning 
two records for the same ISSN? 

 use strict;  
 use Net::Z3950;
 use MARC::Record;
 use MARC::File::USMARC;
 use MARC::Field;
 

my $conn = new Net::Z3950::Connection('z3950.loc.gov', 7090,databaseName => 'Voyager');
my $issn="0896-9205";
my $query = '@attr 1=8 ' . $issn;
$conn->option(preferredRecordSyntax => "USMARC", elementSetName => 'b');
my $rs = $conn->search($query)
        or die $conn->errmsg();
my $n = $rs->size();
 print "found $n records\n"; 

for (my $i = 1; $i <= $n; $i++) {
  my $rec = $rs->record($i)
        or die $rs->errmsg();
my $m = MARC::Record->new_from_usmarc($rec->rawdata());
print $m->subfield('650',"a"), "\n";
#print $rec->render();
}

# perl test.pl
found 2 records
Sociology
Sociology

-- 
Sharif Islam                 Research Programmer
Library Systems Office       University of Illinois Urbana-Champaign
http://www.library.uiuc.edu  phone:  (217) 244-4688