He avoided making a reference to the problem.

He did not refer to that problem.

He seems to be chasing an illusion.

The emergence of that new species of flower surprised the scientists.

A new problem has emerged.

His letter had an emotional postscript written on it.

He added words of gratitude to the letter.

The new era name has been announced.

The police rushed to the actual spot.

I think this prototype will be useful in developing new products.