Self-training is a very prevalent semi-supervised method. Its key idea is to augment the original labeled dataset with unlabeled data paired with the model's prediction (i.e. the pseudo-parallel data). Self-training has been widely used in classification tasks. However, will it work on sequence generation tasks (e.g. machine translation)? If so, how does it work? This blog introduces a work [1] which investigates these questions and gives the answers.