How do I cite / write about something someone has just said during a presentation? I once attended a scientific conference with a few hundred participants. There, the CEO of Frobcorp, Inc.1 gave a keynote speech on what their product is about and how they accomplish certain things.

There is one piece of information that was mentioned during the keynote which is quite important to me. I would like to include it in a paper that I'm writing. (Or in my thesis at a later stage.)

Now, this being a keynote, there were just a few slides with stock photos on them, so I don't have a physical reference to what was said there. I do however know that hundreds of others have heard the same piece of information (unless they were just checking e-mails during the talk).

How should I include this?

Does a sentence like the following make sense, or could it be dismissed for lacking a reference?


  As explained by the CEO of Frobcorp, Inc., during a keynote speech at the ... conference, they do ... to improve their Frobber&trade; product.


I of course understand that this may depend on whatever field of science this is going to be published in, what the conference or journal is, and what my supervisor thinks.

1 Yes, this is completely made-up.
I'd use the form for symposia, adjusted slightly to reflect that it's a keynote speech with only one speaker. 

For the APA style, see the second block in this blog entry:


  Symposia
  
  A symposium is a bit like a live-action edited book: Several authors come together under the leadership of the chair to pool their knowledge about a topic.
  
  Krinsky-McHale, S. J., Zigman, W. B., &amp; Silverman, W. (2012, August).
       &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Are neuropsychiatric symptoms markers of prodromal Alzheimer’s 
       disease in adults with 
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Down syndrome?
   In W. B. Zigman (Chair), 
       Predictors of mild cognitive impairment, dementia, 
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;and mortality in 
       adults with Down syndrome. Symposium conducted at the meeting 
       of the
  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;American Psychological Association, Orlando, FL.