String dataDir = Utils.getSharedDataDir(LoadingNotebookFilewithLoadOptions.class) + "Notebook/";

// By default children loading is "lazy".
Notebook notebook = new Notebook(dataDir + "test.onetoc2");

for (INotebookChildNode notebookChildNode : notebook) {
	// Actual loading of the child document happens only here.
	if (notebookChildNode instanceof Document) {
		// Do something with child document
	}
}