Sentence examples for remain difficult to establish from inspiring English sources

Conversely, long-term health effects such as pneumoconiosis and cancer, which have subtle early detectable symptoms, remain difficult to establish because of the long latency of these diseases.

Whether such cross-sectional association also has prognostic significance over long-term follow-up has however remained difficult to establish, and large prospective studies on early RA are currently not available.

However, the extent of the problem remains difficult to establish.

The contribution of AKI by itself remains difficult to establish.

However, any hypothetical causal relationship remains difficult to establish.

Only recently have techniques for conjugation been established and these remain difficult to control and are of low efficiency [ 8].

His views of the West remain difficult to divine.

Methane and ethane remain difficult to convert by this route.

Many variants remain difficult to classify by traditional genetic methods.

The mechanisms leading to sensory restoration remain difficult to explain.

Questions remain unanswered or factors remain difficult to measure.