Per Year

 @article{stochasticsimulation-jphyschem81,
	Author = {Gillespie, Daniel T.},
	Doi = {10.1021/j100540a008},
	Journal = {The Journal of Physical Chemistry},
	Month = dec,
	Number = 25,
	Pages = {2340--2361},
	Title = {Exact Stochastic Simulation of Coupled Chemical Reactions},
	Url = {http://pubs.acs.org/doi/abs/10.1021/j100540a008},
	Volume = 81,
	Year = 1977} 

 @book{blockworld-book1977,
    apice = {BlockworldBook1977},
    author = {Sacerdoti, Earl D.},
    isbn = {9780444002099},
    isbn-10 = {044400209X},
    issn = {0587-5463},
    lccn = {77023276},
    publisher = {Elsevier},
    series = {Artificial Intelligence Series},
    title = {A Structure for Plans and Behavior},
    url = {https://books.google.it/books?id=sCEZAQAAIAAJ},
    volume = 3,
    year = 1977
} 

 @article{petrinets-csur9,
	acmid = {356702},
	address = {New York, NY, USA},
	author = {Peterson, James L.},
	doi = {10.1145/356698.356702},
	issn = {0360-0300},
	journal = {ACM Computing Surveys},
	month = sep,
	number = 3,
	numpages = {30},
	pages = {223--252},
	publisher = {ACM},
	title = {{P}etri {N}ets},
	url = {https://dl.acm.org/citation.cfm?id=356702},
	volume = 9,
	year = 1977}