1.   Other status groups erect less formidable barriers to entry.

2.   To begin with, these forces have created the most formidable barrier to animal movement on earth.

3.   Whether clipped into shape or left natural, barberry is a formidable barrier thanks to its dense foliage and profusion of thorns.

4.   The mountains were a formidable barrier.

5.   But telemedicine faces formidable barriers to growth as well.

6.   Compounding that problem is the Japanese investment culture, in which long-standing financial and economic relationships between pension funds and their managers remain formidable barriers to entry.

7.   Even after Botero agreed, there were formidable bureaucratic barriers to be overcome.

8.   Harrison and Chapin identified two potential north-south strips of habitat that wolves could use to cross the St. Lawrence River Valley, a formidable barrier.

9.   Of course, details and implementation posed formidable barriers to peace from the start.

10.   Supersonic speed has remained a formidable barrier for most airlines, and no successor to Concorde is within sight.