In this Knowledge base you are going to see te most general aspect on working with combined EEG NIRS registering for your research. Because of the aspects they register and the ease to work with this techniques combined, they are promising in understanding the brain dynamics in cognitive neuroscience. 

You can also find more information on this in some new publications like 

Stuys using this techniques 

https://www.frontiersin.org/articles/10.3389/fnhum.2019.00301/full

And also more in depth information on using this two techniques 

https://pubmed.ncbi.nlm.nih.gov/29060891/