Per Year

 @article{turing-plms45,
    author = {Turing, Alan Mathison},
    doi = {10.1112/plms/s2-45.1.161},
    urlpdf = {http://plms.oxfordjournals.org/content/s2-45/1/161.full.pdf+html},
    journal = {Proceedings of the London Mathematical Society},
    number = 1,
    pages = {161--228},
    title = {Systems of Logic Based on Ordinals},
    url = {http://plms.oxfordjournals.org/content/s2-45/1/161.short},
    volume = {s2-45},
    year = 1939
}