I have been reading through  to get a better understanding of geminal based methods. This is one of two questions that I'm asking about that paper on this site, the other one being: Understanding the complexity of geminal-based wavefunctions. This question is: How does expression (1) relate to Eqs. (3) and (7)?
- P. Tecmer & K. Boguslawski Phys. Chem. Chem. Phys., 2022,24, 23026-23048 DOI