The phrase "a certain copy of" is correct and usable in written English.
It can be used when referring to a specific version or instance of a document, book, or other material without specifying which one.
Example: "I found a certain copy of the manuscript that contained additional notes from the author."
Alternatives: "a specific version of" or "a particular edition of".
The minor expansion of the CDPK family in chromalveolates has created an evolutionary opportunity for certain copies of CDPK genes to subfunctionalize, adapting the additional regulatory role for promoting phosphorylation-dependent inter-domain closure.
Before the mid-18th century, some European wares had found their way to China, as witness certain copies of early Meissen porcelain.
It is currently unclear by what mechanism function is preserved in certain copies of this highly repeated gene family, but not in others.
In 1930 the Polish mathematician Kazimierz Kuratowski proved that any nonplanar graph must contain a certain type of copy of K5 or K3, 3.
A handful of titles have already benefitted from this new structure, and in the coming months there are many more albums that will be certified, despite their not having actually sold a certain amount of copies.
The first are highly skilled self-promoters like Godin who have successfully identified their entire (niche) audience and who know they will only ever sell a certain number of copies of their books to that same audience.
They asked for a certain number of copies and focused on a certain style.
Furthermore, it was made a limited release because Swift only allowed Big Machine Records to manufacture a certain number of copies of the EP.
The anthology was published by Fortune Press, in part a vanity publisher that did not pay its writers and expected them to buy a certain number of copies themselves.
Once a certain number of copies of the transposon are established in the genome, and the transposase concentration is above a critical threshold, the mechanism provides a steady-state rate, perfectly damping the exponential amplification which is a natural consequence of unregulated transposition.
