Effective semi-supervised learning algorithms based on pretraining techniques (Hinton and Salakhutdinov, 2006;Bengio et al., 2007;Erhan et al., 2010) have been developed for text classification, deep belief networks (Hinton and Salakhutdinov, 2006), and stacked autoencoders Bengio et al., 2007).
dai and Le (2015) developed an autoencoder for the later supervised learning process.