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| Buy tickets at ATM (by 10 it's much cheaper)... | 
...because counter is often closed! (Here, Denfert-Rocheau) | 
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| RER B Denfert-Rochereau platform | 
It is better to ride at the train front outdoor | 
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| check at the display that the train stops at Massy-Palaiseau (this one is not) | 
... or Lozere (Ecole Polytechnique) if you want to climb the hill (this one does both) | 
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| TV displays indicate trains bound for Massy-Palaiseau and Saint-Remy (Ecole Polytechnique)  | 
Get off the train at Massy-Palaiseau at the front of the train, climb the staircase | 
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| Turn slightly to the left to exit the corridor and... | 
... go down the staircases to go the the 91.06 bus stop | 
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| Wait in front of  the 91.06 bus stop... | 
...You need to use another ticket (Buses always stop at Ecole Polytechnique) |