That was the most difficult and a very challenging period of my tenure here.

After their deaths the brewery began its first of many economically challenging periods.

Mr. Bush is hardly the first president to go before a friendly crowd during a challenging period.

"This has been a very challenging period for the whole of the industry, which has faced fierce competition."

"We are on the brink of our most challenging period," he said.

Well, possibly, except that winter, for seasonal purists, really is a challenging period to get through.

It's a challenging, but exciting period for young researchers.

"2003 will be the most challenging period of the postwar era for Germany."

"I have been with Franklin since 1989, and this was one of the most challenging periods on record," he said.

They try to make it through the challenging period.