The factors controlling hepatocyte proliferation are complex and incompletely understood.

My reasons for this preference were complex and incompletely understood.

Also, there is a wide range of incompletely understood phenomena in astronomy.

It was still mysterious in many ways, still incompletely understood.

The feedback mechanisms involved are often complex and incompletely understood.

Details of its chemical make-up and formation are still incompletely understood.

The causes are incompletely understood at the present time.

Calcicludine has a unique mode of action, which is still incompletely understood.

Glaciation has played an important but incompletely understood role in the park.

Similar to many general anesthetics, how isoflurane works remains incompletely understood.