not certain

References in classic literature ?
My friend has an excellent understanding-- though I am not certain that I consider her marrying Mr.
They had not met for two or three weeks, and Mary had much to say to Ralph; but she was not certain how far he wished for her company.
Becky supposed she would be glad of that, and she tried to believe she was glad of it, but she found she was not certain.
But it is not only that which drives me to despair; for what I am not certain of, madame, is that the man whom Christine loves is worthy of her love
I did not know that; I am not certain that I know it now.
She was not certain where he lived, but it was in one of the three houses opposite.
However, it is not certain that Halpin Frayser came to his death by exposure.
Still it is thought, though it is not certain, that we occasionally see the actual surface of this orb, an advantage we do not possess as respects any other of the heavenly bodies, with the exception of the moon and Mars.
I am not certain of that,' rejoined Doyce, laying his hand persuasively on his shoulder.
We discussed everything we knew, during the first fifteen or twenty minutes, that morning, and then branched out into the glad, free, boundless realm of the things we were not certain about.
I'm not certain," said Rebecca conscientiously, "but I'll look in the circular--it's sure to tell;" and she drew the document from her pocket.
And it is not certain, that with this aid alone they would not be able to shake off their yokes.