on his students' notes/in
 

John is a student studying mathematics at university. Every week before the lecture, the lecturer will upload a PowerPoint file onto the online system accessible only to students enrolled in the course. The PowerPoint files will contain the important things the lecturer is going to talk about in the lecture. On/in those slides, students will find point forms or complete paragraphs. Is it correct to say

-On John's students' notes, he will find all the important information he needs to write the mid-term essay.

ON sounds wrong to me and IN should be used. Do native speakers agree?

Re: on his students' notes/in
 

On or In is fine for the slides. If they were being projected on the wall, on a sreen I'd probably use "on", but "in" wouldn't be wrong. If they were printed out and distributed on paper then my preference would probably be "in".

However, with "notes" the preposition would definitely be "in".

On + physical object : on paper / on the slides / on the screen / on the wall / on the page

In = contained in the middle of some information : in his speech / in the summary .
Notes are information rather than a physical object so "in" must be used

Slides can be seen as physical "things" ie the container of the information - so "on", or as the information itself - so "in". The same with things like leaflets and handouts : You'll find the name somewhere in/on the leaflet/handout

Re: on his students' notes/in
 

Thank you.