Update week15.do.txt

Author: mhjensen

doc/src/week15/week15.do.txt

@@ -12,7 +12,8 @@ o Variational Quantum Circuits (VQCs)
 o Quantum neural networks (QNNs)
   * Training QNNs and Loss Landscapes
   * Implementing QNNs with PennyLane
-o "Video of lecture at":"https://youtu.be"
+o Video of lecture, first part at URL:"https://youtu.be/L9kvkEW1ZgQ"
+o Video of lecture, second part at URL:"https://youtu.be/L9kvkEW1ZgQ"
 o Whiteboard notes at URL:"https://github.com/CompPhysics/QuantumComputingMachineLearning/blob/gh-pages/doc/HandWrittenNotes/2025/NotesMay7.pdf"
 !eblock