1.   The expedition Marked a milestone in the history of exploration.

2.   This time it was to mark a milestone in the history of exploration.

3.   George, marked the milestone on Thursday with friends and staff.

4.   As they gathered with family and old friends to mark the milestone, people like Bailey were ambling about, looking for a taste of what they had lost.

5.   At the very least, the opening of the Wolfsonian marks a milestone in the maturity of the Information Age.

6.   A PRI loss of control over the house would mark a milestone in Mexican politics.

7.   But each marked a milestone in a history of almost constant struggle, and each created a new distribution of power, geography and grievance.

8.   But its release marks a milestone in the history of cancer drugs, raising the bar for future research and development.

9.   But unlike their parents and grandparents, baby boomers marking the milestone are more likely to regard it as no big deal.