Text and Data Mining valid from 2019-04-15
First Online: 15 April 2019
Compliance with ethical guidelines
: Y. Huang, J. Yin, Z. Sun, S. Song, Y. Zhuang, X. Liu, S. Du and Y. Rui declare that they have no competing interests.
: For this article no studies with human participants or animals were performed by any of the authors. All studies performed were in accordance with the ethical standards indicated in each case.