Hi @Dewbob,
A few things to consider, in addition to the wonderful input in this thread:
A simple, shorter stack you will listen to consistently is always a good starting point for consistent results.
The format below is always helpful for making your stacks more effective.
Neurotransmitters affect each person differently to some extent, depending upon your neurochemistry and current state of being.
For example, some may respond differently to the same neurotransmitter field. And different amounts of listening for different durations may be optimal for each person and their goals.
So try the fields and see how you go with them, then adjust your listening. 
That said, acetylcholine will certainly aid memory retention and information acquisition for most.
Memory retention and access is complex. There are many possible fields. BDNF and the basic stack recommended above will certainly help.
Brain Regeneration is always excellent.
As @_OM put it,
Superhuman Genius creates a charged brain with a lot of growth potential and plasticity, amongst other things. Listening before studying is fine. The potential lasts for some time.
If you are considering a paid field such as Brain Growth Work, you might consider the Cognitive and Memory Enhancement tag, which contains the previous Memory Enhancement field.
The description of that field is below and may contain some insights of interest to you.
The ability to remember and repeat information is perhaps one of the most important abilities in our time. We record information constantly and need this information to go about our daily lives efficiently.
Telephone number, Personal Identification Numbers for accounts, addresses and names all play a part in our daily lives. Add to that the avalanche of information about new technologies and socio-political information and it is a wonder we manage to ever remember to pick the kids up from school!
This item doesn’t just help with memory however! It allows you to access and utilize memory better, that’s true, but it also improves all of your mental faculties at the same time!
There is a lot that goes into such an item, but the main points (and field sets) are as follows:
Specific fields in this item
Subconscious Repetition: When you encounter new information, your subconscious mind will prompt you to refresh your working memory several times, helping to drive the new data deep into your long term memory. *Yes, you can do this yourself, using conscious effort, and you should! The specific pattern that helps most is to refresh the memory at these intervals: Three seconds after first exposure, one minute, two minutes, twenty minutes, 24 hours and 72 hours. If you hit a repetition at all those points you will retain that information for roughly 20 years. This field just makes doing so a bit easier.
Enhancement of the Hippocampus: This field simply aids your body in increasing the activity level and sensitivity in this specific area of the brain. This will tend to aid in memory functions, both in retrieval and formation of long term memories.
Pre-Frontal Lobe Enhancement: This is the area of the brain that holds your specific attention in the given moment and memories lasting less than three seconds. By increasing the blood flow and activity of this area, your attention span increases and your ability to focus will more than double instantly, even without trying. If you make an effort, this set of abilities will increase far more dramatically. It still takes effort, but your return for that effort will increase exponentially!
Myelin Sheath Production: By increasing the production, along the normalized, pre-established patterns of the brain, of this compound, the insulation value of each nerve strand goes up, preventing signal lose! It has recently been determined that one of the major factors in human intelligence is this insulation. The more you have of it (In general, there is most likely a highest effective level as there is in most things, though this has not been determined at this time) the more intelligent you are. It’s that simple and this field will cause your brain to develop thicker and healthier myelin sheaths over time.
Global Integration in Processing: Having good recall is not the whole of intelligence, obviously! The ability to put information together does require you to have access to that information, but Global Processing, or Whole Brain Thinking allows you to use more of your potential processing power, put things together in unique ways that may have been otherwise missed and allows you to bend your personal rules of intelligence enough that you can entertain things in new dimensions.
Being intelligent and remembering new information still takes an act of will. You have to choose to use these things. This item will just give you a chance to use what you already have at a much higher level.
Finally, consider other factors, such as your mental clarity and your energy levels if studying for long periods of time, as this can affect your memory retention significantly as well.
Information processed in a clear state of mind, or with greater understanding, will be retained far better than that processed when you are unclear or tired.
So one could consider adding a field like Plasma Charged Mitochondria and/or Induced Mots-c Production for energy when needed.
Five Elements Balanced (Mongolian Medicine) can be another excellent field to balance your state of being, clarity and potential which some may not consider in this situation!