This week's book giveaways are in the Jython/Python and Object-Oriented programming forums. We're giving away four copies each of Machine Learning for Business: Using Amazon SageMaker and Jupyter and Object Design Style Guide and have the authors on-line! See this thread and this one for details.
Are you using a particular methodology? That very much drives how you approach requirements.
I like how Larman's approaches this in his "Applying UML and Patterns".
Wikipedia is also a starting point to find your way.