I have alluded to

Lucy, this note may seem mysterious; but if it shall, I did not mean to make it so; nor do I know that I could have helped it. But the only reason is this, Lucy: the matter which I have alluded to, is of such a nature, that, for the present I stand virtually pledged not to disclose it to any person but those more directly involved in it.
--Herman Melville, Pierre; Or, The Ambiguities (1852) .

My tragedy is all true,--and if not quite serious, has, as is proper, its moral;--but rather, as I have alluded to the primitive tragedy....
--Scenes Beyond the Western Border (March 1853); and Scenes and Adventures in the Army.