How to cite class notes in a paper?
If you cannot find the material in a more "official" source, such as a peer-reviewed journal or conference paper, then you should check with the publisher on how to cite the lecture notes directly. 

If allowed, the exact way to cite the lecture notes will depend on the citation guidelines where you are submitting. For example, in IEEE citation format, I am aware of a couple of acceptable citation formats for citing lecture content. 


This IEEE citation example is taken from here:



  S. Maw. Engg 251. Class Lecture, Topic: “Speed skating.” ICT 224, Faculty of Engineering, University of Calgary, Calgary, Alberta, Oct. 31, 2003.



This example is taken from here:



  S. Bhanndahar. ECE 4321. Class Lecture, Topic: “Bluetooth can’t help you.”
  School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, Jan. 9, 2008.


It is interesting to note that a quick check of the official IEEE Citation Reference does not mention the correct format for citing class/lecture notes. So you may need to dig around a bit to find the correct format for wherever it is you are submitting.