@article {hu2015recent,
	title = {Recent progress in piezoelectric nanogenerators as a sustainable power source in self-powered systems and active sensors},
	journal = {Nano Energy},
	volume = {14},
	year = {2015},
	pages = {3{\textendash}14},
	publisher = {Elsevier},
	author = {Hu, Youfan and Wang, Zhong Lin *}
}
