1.   He called on citizens to do their part to fight crime and help the police.

2.   I expect that he will do his part to fulfil the agreement between us and him.

3.   I had a day off so I took the train down and did my part.

4.   Loss of momentum occurs when other people are not motivated to do their part.

5.   Wimpey and the other opencast producers are fighting this, but you have to do your part.

6.   Of course, integrated programmes are less suitable for part-time attendees and those who want to do parts of a modular programme.

7.   In all three cases, it seems hard to conceive helping in any other way than as doing part of the activity denoted by the infinitive oneself.

8.   Malcolm was doing part of it.