Citations not collapsing
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For example, the two cites in the citation "(Hasan et al., 2008a,b)" link to the papers
Hasan, K.M., Ewing-Cobbs, L., Kramer, L.A., Fletcher, J.M., Narayana, P.A., 2008a.
Diffusion tensor quantification of the macrostructure and microstructure of human midsagittal corpus callosum across the lifespan. NMR Biomed. 21, 1094–1101.
Hasan, K.M., Kamali, A., Kramer, L.A., Papnicolaou, A.C., Fletcher, J.M., Ewing-Cobbs, L., 2008b. Diffusion tensor quantification of the human midsagittal corpus callosum subdivisions across the lifespan. Brain Res. 1227, 52–67.
This is now cleared up, but we have one more question. What happens if two papers are cited for which the first authors have the same family name, but different given names? For example, consider we have one paper written by A. Hasan, and one by B. Hasan. If these two papers are cited together, do we still have collapsing, with the result "(Hasan 2008a,b)"? Some styles add initials to disambiguate the names: "(A. Hasan 2008, B. Hasan 2008)". Alternatively, you could use "(Hasan 2008a, Hasan 2008b)", where you separate the names but don't disambiguate them. Do you know how the Elsevier journals handle such cases?