What is the fine-grained topic of the following text: After attaining enlightenment, Sravaka-Buddhas might also lead others to enlightenment, but cannot teach the Dharma in a time or world where it has been forgotten or has not been taught before, because they depend upon a tradition that stretches back to a Samyaksam-Buddha. Only return the topic.
Limitations of Sravaka-Buddhas in Teaching Dharma