>> (does it named 'vertex animation'?),

mesh morphing might be more precise.

if its the method i think you're talking about, basically every frame (or keyframe if you tween) is a copy of the mesh in a different pose, usually set via a skeleton in a modeling package, then exported without the skeleton. as you can imagine, this is a rather data intensive way to do things, having multiple copies of the mesh in the animation data.

>> I can't find any of source, instructions

what are you using for skinned meshes with skeletons? home rolled code? if so, odds are you'll end up rolling your own for this too. many shops roll their own solution for animated meshes - or simply rely on a 3rd party engine or middleware library. i used DX sample code to make a skinned mesh middleware library for dx9. if i was supporting mesh morph animation, i'd roll my own if no turn key or near turn key official sample code existed.

While assimp does support "mesh morphing" (or per-vertex) animation, almost no modeling software nowadays will produce animation data in that way for keyframed animations. Non-skeletal animation will simply animate the scene nodes by 3 channels (translation, rotation, and scale). There isn't any skinning so there will be no vertex weight data like there is with skeletal animation, but otherwise it's pretty much the same thing.