You can look at Yoshua Bengio's Google Scholar profile [1] and scroll down to see what they were working on around that time.

Here are some papers with many citations:

- An empirical evaluation of deep architectures on problems with many factors of variation [2]

- Extracting and composing robust features with denoising autoencoders [3]

- Scaling learning algorithms towards AI [4]

[1] https://scholar.google.com/citations?hl=en&user=kukA0LcAAAAJ...

[2] https://scholar.google.com/citations?view_op=view_citation&h...

[3] https://scholar.google.com/citations?view_op=view_citation&h...

[4] https://scholar.google.com/citations?view_op=view_citation&h...