We believe this plan does not adequately consider the challenges to U.S. security that may arise in the next century, and the central role that the B-2 may play in meeting those challenges.

CENTERFORSECURITYPOLICY: Letter to the President

One of the biggest challenges was writing software to integrate ADS-B with an older, less sophisticated collision-avoidance system.

FORBES: Technology

Just as a virus that affects humans can mutate and confound medical experts, each version of Sasser -- labeled A, B, C, and D -- poses slightly different challenges for information technology experts.

CNN: Sasser worm rips through Internet

Triestina, which plays in Serie B, the second tier of Italian soccer, has some serious challenges when it comes to selling tickets.

WSJ: Italian Soccer Team Employs Fake Fans

You may need him or her later on if the other side challenges how you got from Point A (tons of collected electronic data) to Point B (production of a much smaller subset).

FORBES: Written by Robert D. Brownstone