Many but not all ETF strategists use backtesting, and investors who are accustomed to mutual funds, where regulations generally forbid this practice, need to be on guard against it, experts say.

WSJ: When Cheap Funds Cost Too Much

But she warned members of the public to be on their guard against the virus.

BBC: Flu rate 'at record low'

You have to be constantly on your guard against being robbed, beaten or dragged into cars by strangers.

BBC

Governments spend vast sums on defence to guard against the remote chance that their countries may be invaded.

ECONOMIST: The case for pre-emptive action

Families should be on the lookout, and work with experienced legal and financial professionals, to help guard against financial exploitation.

FORBES: 4. Arturo Gatti