@article{Gilbert1958, 
     author = "Gilbert, E. N.", 
     doi = "10.1002/j.1538-7305.1958.tb03887.x", 
     journal = "Bell System Technical Journal", 
     link = "http://ieeexplore.ieee.org/articleDetails.jsp?arnumber=6773372", 
     month = "may", 
     number = "3", 
     pages = "815--826", 
     publisher = "Alcatel-Lucent", 
     title = "Gray Codes and Paths on the n-Cube", 
     uri = "http://ieeexplore.ieee.org/articleDetails.jsp?arnumber=6773372", 
     volume = "37", 
     year = "1958", 
}

Problems: 427