Of course much may be said
Of course these remarks hold good
Of course we may, if we please
Of course you will sympathize
Of one thing, however, I am certain
Of this briefly
Of this statement I will only say
Of this truth I shall convince you by
On a review of the whole subject
On occasions of this kind
On such a day as this
On the contrary, I am assuming
On the occasion to which I refer
On the other hand, it is clear
On the whole, then, I observe
On this auspicious occasion
On this point I do not mean to dwell
On this subject you need not suspect
Once again, there are those
Once more I emphasize
Once more let me try to put into words
One additional remark
One almost wishes
One can not decline to note
One concluding remark has to be made
One fact is clear and indisputable
One further word
One important topic remains
One is fairly tempted to wish
One lesson history may be said to repeat
One might be challenged to produce
One of the ancients said
One of the most commonly known
One of the most extraordinary incidents
One of the things I recollect with most pride
One of these signs is the fact
One or two points are made clear
One other circumstance
One other remark suggests itself
One remark I will make
One thing more will complete this question
One thing which always impressed me
One very striking tendency
One word in courtesy I must say
One word more in a serious vein
One would naturally suppose
Only so much do I know
Opinions are divided as to whether
Or to come nearer home
Or to take but one other example