This course is based on these two manuals. The discussion topic is also from my knowledge of growing and caring for a large home orchard, other research and talking with experienced citrus grove growers.
Manual Circular 409:
https://archive.org/details/citrusfruitforho40953john/mode/2up
A Manual for Citrus Growers 1951: (I own this book, download at your discretion)
https://mewsie.org/textbook/a-manual-for-citrus-growers/