And regulation, while essential, can never be perfect.
Their teachers' patience and understanding, while essential, could prove insufficient.
While essential, revocation checking can leak potentially sensitive information.
"Dealing with greenhouse gases, while essential, is very costly," Mr. Rowe said.
Shielding the military and the health service, while essential, required cutting more recklessly elsewhere.
But Republican strategists say that the same-sex marriage amendment, while essential to conservatives, has much broader appeal.
Here's the million-dollar health supply chain question: how does Coca-Cola get to remote villages while essential medications can't?
Ceremonies of remembrance, while essential, unintentionally reinforce the widening gap between those in uniform and the rest of society.
They are complementary players, and complementary players, while essential to a team's success, come a dime a dozen.
Many of the company's patents, while essential to BlackBerry itself, cover technologies that may be near their expiration dates.
The role of molecular methods is controversial for the diagnosis of FIP, while essential for the identification of the shedders.
