The transport sector is a principal source of global emissions of greenhouse gases.

ECONOMIST: The future of energy

Can we responsibly continue for another generation to lock our transportation sector (the principal, and most profligate, consumer of imported oil) into dependence on oil substantially imported from unfriendly places?

CENTERFORSECURITYPOLICY: Set America Free

The official sector, by contrast, holds principal highly sacred.

FORBES: Eurozone: How They Really Solved The Greek Debt Problem

In a submission to the committee, Edinburgh College principal Mandy Exley warned the pace of cuts to the sector could create a "funding crisis" and staffing problems.

BBC: Part-time Scottish college places cut, say principals

Principal Muscatelli, who has told his staff that public sector cuts could see the university lose about 8-10% in funding, said a contribution from graduates may be needed to help combat the cash "crisis".

BBC: Glasgow University principal says consider graduate tax

My vote for the most unjustly maligned financial sector stocks goes to the bond insurers, which guarantee principal repayment and interest for most municipal bonds.

FORBES: Buy Some Insurance

In case you have forgotten during the turmoil of what has since transpired, Greece's private-sector lenders agreed in the spring to let the Greek government off around 100bn euros of principal repayments.

BBC: Greece: Euro exit delayed?