Certainly not a final answer... but... it seems to me that no matter what standard you choose, there will always be some suppliers that do not have immediate access to it. I would recommend that you choose some standard that is recognized, or at least commonly referenced, in the majority of countries in which your suppliers operate. Place some notification on your drawings (in bold print) that it is the supplier's responsibility to assure that he is meeting the stated standard. Prepare your purchasing folks to be ready to respond to inquiries with recommended sources where the suppliers can obtain copies of the standard.