Update links-to-lessons.md

Author: rkhetani

schedules/links-to-lessons.md

@@ -76,3 +76,7 @@ Download the most recent versions of R and RStudio:
 * [base R cheatsheet](../img/base-r.pdf)
 * [RStudio cheatsheet](https://rstudio.com/wp-content/uploads/2016/01/rstudio-IDE-cheatsheet.pdf)
 * [ggplot2 cheatsheet](https://rstudio.com/wp-content/uploads/2015/03/ggplot2-cheatsheet.pdf)
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+****
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+*These materials have been developed by members of the teaching team at the [Harvard Chan Bioinformatics Core (HBC)](http://bioinformatics.sph.harvard.edu/). These are open access materials distributed under the terms of the [Creative Commons Attribution license](https://creativecommons.org/licenses/by/4.0/) (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.*