know that you've seen the particular video, have you seen evidence that an sa-11 or buk missile system would cross the border at some point from russia into ukraine, and what can you tell us about that system and the sophistication and training that would be needed by russian separatists to actually be able to operate it effectively? >> i don't have specific information about a buk system making that transit. we're not ruling anything in or out at this point. it is -- it is a sophisticated -- that said, it is a sophisticated system. the missile itself, the saa 11, which is the one we believe was used to down flight 17, is a sophisticated piece of technology. and it -- it strained credulity to think it could be used by separatists without at least some measure of russian support