Based on this comment from fluffypony it appears that MRL-007 was skipped and does not (currently) exist.

@kenshi84 any chance you could do a formal write-up and submit it to the Monero Research Lab repo for us to publish? It would go as MRL-0006, and the current WIP that is MRL-0006 would be moved out to 7 or something.

@kenshi84 confirmed a willingness to begin working on a formal write up (to become MRL-006) for the topic in the one-time receiving address idea that led to this pull request

@fluffypony Sure, I'd be honored to be able to publish at MRL:)

The previous MRL-006 will be renamed MRL-007 and Difficulty Adjustment Algorithms in Cryptocurrency Protocols research will continue.