date_time giving undefined references

Hello,

I am trying to compile a simple example using the parsers and formatters
of the date_time library using g++ under Cygwin.  I can successfully
build other boost examples passing only the include directory to g++,
but all date_time ones that I have tried fail.

#include <boost/date_time/gregorian/formatters.hpp>
#include <boost/date_time/gregorian/parsers.hpp>
#include <boost/date_time/gregorian/greg_date.hpp>
#include <iostream>

using namespace boost::gregorian;

int main()
{ 
 std::string s("2001-10-9"); //2001-October-09
 date d(from_simple_string(s));
 std::cout << to_simple_string(d) << std::endl;
 }

$g++ -I/usr/include/boost-1_33_1 -o example example.cpp

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boost::date_time::month_str_to_ushort<boost::gregorian::greg_month>(std:
:basic_s
tring<char, std::char_traits<char>, std::allocator<char> >)]+0x102):