Garcia-Garcia L A, et al. (a) (B) (c) (D) (e) (F) Figure 2. Keyword co-occurrence network maps: (a) APY 2011, (B) APY 2012, (c) APY 2013, (D) APY 2014, (e) APY 2015, and (F) APY 2016. International Journal of Bioprinting (2018)–Volume 4, Issue 2 5