The phrase "about their extent" is correct and usable in written English.
It can be used when discussing the range, scope, or limits of a particular subject or topic.
Example: "The researchers published a paper discussing the implications of climate change about their extent on global ecosystems."
Alternatives: "regarding their scope" or "concerning their range".
Undoubtedly, there are some cleavages, but observers of the Taliban disagree about their extent.
Others accept that buy-backs are a legitimate way to return cash to shareholders but worry about their extent.
But I do want the right, as a citizen, to know and decide about their extent, severity and duration.
In addition to inspecting and monitoring these risks, regulators now face the challenge of keeping the public well informed about their extent.
The foci in both IPa and TEa were partly composed of isolated fields of green or red neurons; but for about half their extent, green and red neurons were intermixed, and there were also some DL neurons.
However, little is known about their actual extent of use in industry.
The theory had been proposed by Lewis as the literal truth, but by treating it as a mere fiction Rosen provided a ready-made story about possible worlds, their extent and nature.
Great Rift, in astronomy, a complex of dark nebulae that seems to divide the bright clouds of the Milky Way Galaxy lengthwise through about one-third of their extent.
They plan to ask Mr. Farmer and Justice Verniero, along with dozens of other law enforcement officials, about their knowledge of the extent of racial profiling and their efforts to eradicate it, including the handling of the case against Troopers Hogan and Kenna.
No other book I know conveys so well the in-depth knowledge which traditional hunter-gatherers have about their environment, and the extent to which they learn from the animals they hunt.
The Evening News quoted Gavin Corbett, a Scottish Green party councillor, as saying: "My understanding is that all 17 schools have issues about their construction to some extent but that the scale of those problems and the consequences vary school to school.
