15 16 Several candidate genes or single nucleotide polymorphisms have been investigated to explain familial clustering of cerebral palsy, 17 18 with extensions to interactions with clinical factors and other genes, 19 although positive findings have proved hard to replicate.
These will prove hard to replicate in other parts of the company.
And the Great Depression that followed the 1929 crash fostered a climate for reform that has proven hard to replicate.
America's shale-gas success a matter not just of helpful geology and Yankee ingenuity, but also of various legal and regulatory positions such as those of the 1978 act may prove hard to replicate in some other countries.
Still, such results have proven hard to replicate.
Though the president won there in 2008, that victory could prove hard to replicate.
However, his methods proved difficult to replicate.
But Africa has proved harder to treat.
This proved hard to arrange.
The question has proved hard to answer.
