Paper  bibtex   

@article{acker_structure_1998,
	title = {Structure and yield of two-aged stands on the {Willamette} {National} {Forest}, {Oregon}: implications for green tree retention},
	volume = {28},
	url = {http://andrewsforest.oregonstate.edu/pubs/pdf/pub2528.pdf},
	number = {5},
	journal = {Canadian Journal of Forest Research},
	author = {Acker, Steven A. and Zenner, Eric K. and Emmingham, William H.},
	year = {1998},
	keywords = {AND, silviculture}
}