MLA

Derby, George Horatio, 1823-1861. Sketch of General Riley's route through the mining districts : [of California] July and Aug. 1849 / copied from the original sketch by Lt. Derby in the office of the 10t. Military Dept. by J.Mc.H. Hollingsworth, Asst.. BRBL_00615. 1850]. https://collections.library.yale.edu/catalog/15821488.

APA, 6th edition

Derby, George Horatio, 1823-1861. (["BRBL_00615"])(1850])[Sketch of General Riley's route through the mining districts : [of California] July and Aug. 1849 / copied from the original sketch by Lt. Derby in the office of the 10t. Military Dept. by J.Mc.H. Hollingsworth, Asst.]. https://collections.library.yale.edu/catalog/15821488.