I am trying to find papers that describe constant low-thrust spiral up-coast-spiral down phasing maneuvers for circular and non-circular orbits. The thrust is assumed to be fixed at $T_{const}$ when the engine is turned on and $0$ when the engine is turned off during the coast phase.

### Circular Orbits ###
The related question https://space.stackexchange.com/questions/46761/phasing-maneuvers-methods-to-travel-between-satellites-with-very-similar-circul contains an excellent [answer](https://space.stackexchange.com/a/46787/42304) that describes a low-thrust spiral up/down maneuver for a perfectly circular orbit.

**Q1:** Is there a reference to learn more about this method for low-thrust circular orbit phasing?

### Non-circular Orbits ###

The closest I could find were these two papers:

 - [Analytic Orbital Averaging Technique for Computing Tangential-Thrust Trajectories by Gao and Kluever (2005)](https://arc.aiaa.org/doi/10.2514/1.14698)
 - [Small Satellite LEO Maneuvers with Low-Power Electric Propulsion by King, Walker, and Kluever (2008)](https://arc.aiaa.org/doi/abs/10.2514/6.2008-4516)
 
**Q2:** Is there a different reference that contains a simpler description of a spiral up-coast-spiral down maneuver that can be used for low-thrust non-circular phasing with $e \approx 0.2$ ?

I'm basically trying to find the papers that people in the industry refer to for low-thrust phasing in the preliminary design stage. Analytic methods are preferred. Any references and insights would be deeply appreciated!