The linked data movement is a relatively new trend on the web that, among other things, enables diverse data providers to publish their content in an interoperable, machine-understandable way. Libraries around the world appear to be embracing linked data technologies that render their content more accessible to both humans and computers. This paper focuses on linked data URIs that refer to authority data. We attempt to identify the specific MARC fields that are capable of hosting linked data information. Additionally, seven major national libraries are examined to determine to what degree they have adopted the fundamental linked data principles.