The links are to fairly elementary presentations. In respect of Va, one needs to keep in mind that the certification doesn't look solely at pitching manoeuvres. Each primary control is examined and the critical manoeuvre (ie giving the lowest speed) for loading defines Va.
Generally pitching manoeuvres may be limiting, but not always so. The early HS125s, as I recall, were limited by rudder and yaw response.
For current FAR23 standards, for instance, the value must be at least the pitching limit, but need not exceed Vc.
Keep in mind, too, that the standards vary over the years, in line with technological capabilities, so that a particular rule for an old aircraft may be quite different to the much newer machine.