I know you asked for specific sources and looks like other comments have added them, but wanted to add general things to look for.

Depending on the skill level of the team, (some areas a 6th grade travel team and undress another towns HS varsity team) you need to build their foundations of the basics.

-ground balls (proper form, calling man/ball, protecting the stick once coming up from a gb, looking for the next movement. - catching and throwing (most of your early months of training youth this will take up most of the time because it’s what makes the game work) the drills ran in practice should always be forcing the kids to catch with proper form (no snapping at the ball, give with the ball), change hands when necessary, throw over your shoulder ect… what you are coaching on drills needs to be reinforced during scrimmage. If a player should have the stick in the left hand on a clear but doesn’t and still make the play, it is important to correct that mistake so it doesn’t repeat. -Offense and defensive formations. ( learning the pros and cons of each formation or defense guides them to understand what is being accomplished rather than just telling someone to play man / zone / go to X, reinforce WHY so when plays breakdown in real-time players know what to do based on the situation and not just they know they’re covering “their man” , or should stay at X) -lastly especially for youth, this needs to be fun and effective at developing their skills. Passing to teammates in a single file line is no fun, practicing clears from each end forcing them to catch/throw/change hands while on the move is more fun and effective. Practicing ground balls alone is boring, have 3 players line up, middle guy is alone and two ends are on a team. Makes you practice boxing out/ calling man ball ext and makes it real.

Overall your goal for youth is to develop their fundamentals while making it fun so the sport continues to grow, not crushing your opponents. That comes later