EN 934-1 is the European baseline. ASTM C494 (US) is similar but not interchangeable. If working globally, you need both — but neither is free.
Go to the BSI Shop (shop.bsigroup.com) or your national standards body. bs en 934-1 pdf free download
The primary source for British Standards is the BSI Shop. Purchasing the document ensures you EN 934-1 is the European baseline