  Existing NFTs confront restrictions of \textit{one-time incentive} and
\textit{product isolation}. Creators cannot obtain benefits once having sold
their NFT products due to the lack of relationships across different NFTs,
which results in controversial possible profit sharing. This work proposes a
referable NFT scheme to extend the incentive sustainability of NFTs. We
construct the referable NFT (rNFT) network to increase exposure and enhance the
referring relationship of inclusive items. We introduce the DAG topology to
generate directed edges between each pair of NFTs with corresponding weights
and labels for advanced usage. We accordingly implement and propose the scheme
under Ethereum Improvement Proposal (EIP) standards, indexed in EIP-1155.
Further, we provide the mathematical formation to analyze the utility for each
rNFT participant. The discussion gives general guidance among multi-dimensional
parameters. To our knowledge, this is the first study to build the referable
NFT network, explicitly showing the virtual connections among NFTs.
