Sentence examples for remained a challenging from inspiring English sources

However, the regularity of the free boundary remained a challenging open problem.

However, achieving high CO selectivity with supported Ru catalysts has remained a challenging task.

Evaluating ecological processes that assemble local animal communities from available species pools has remained a challenging task.

The remediation of petroleum hydrocarbon-contaminated soils has remained a challenging issue for environmental scientists and engineers.

However, such integration has remained a challenging task due to the temporal changes of environmental processes and the static nature of GIS.

Last week Merlin warned that London, where it owns Madame Tussauds and the London Dungeon, remained a challenging market despite the advantage of a cheaper pound potentially attracting more tourists.

But moving remained a challenge.

Food remained a challenge throughout.

Defining the best chemotherapy combination has remained a challenge.

But producing such filters with controlled pore sizes has remained a challenge.

Residents have been receiving bottled water, but as of last week distribution remained a challenge.