Sentence examples for it is frequently very difficult from inspiring English sources

Practicing chemists soon learn, often simply by experience, that it is frequently very difficult to crystallize a newly synthesized substance, while subsequent crystallizations are considerably more facile.

The separation or, much more difficult, the quantification of the effects of the two pathogenic factors is frequently very difficult or impossible.

Placing an implant in the maxillary molar area is frequently very difficult due to the limitation in terms of the quality and quantity of the alveolar bone of the maxilla [9].

Hierarchy in evolution is commonly presented in phylogenetic diagrams, and the ability to comprehend evolutionary relationships has come to be referred to as "tree thinking," which many authors argue is frequently very difficult to grasp and to teach (Baum and Offner 2008; Gregory 2008; Sandvik 2008; Meisel 2010).

But it is frequently very, very difficult to get good monitoring to be implemented in practice.

"This is frequently a very difficult disease," Dr. Brawley said, "but the outlook for someone who has early stage pancreatic cancer can be very good".

It is very, very difficult.

So it is a very difficult judgment.

"It is difficult, very difficult.

It is not very difficult.

"It is a very difficult question.