Federal officials have sometimes used local investigators on joint terrorism task forces to conduct library inquiries.

If they don't reopen the whole thing now and actually use outside investigators, this will be like the Kennedy assassination for the next 50 years.

"I understand we've used search agencies, but not private investigators," he adds.

The article says that the three business schools recently began using private investigators to verify the work experience listed in all their candidates' applications.

By 2002, the practice of publications using private investigators to acquire confidential information was widespread.

She does not know of any students' using investigators, she said, "but I would recommend it to my classes."

He added that when a company was found to be using private investigators to harass unwanted employees, "we'll walk away."

She also says that she has not used private investigators for some time.

He says if it uses private investigators in future, the paper will need a formal agreement with them and this is "just good practice".

"Certainly in my time, we have not used private investigators," he says.