Part,  Chapter, Paragraph

1   II,     9.  1.  1|  Joseph KS, Demissie K, Vintzileos AM (2005): Trends in twin
2   II,     9.  1.  1| Smulian J, Harrigan JT, Vintzileos AM (2004): Maternal age
3   II,     9.  3.  2|  Joseph KS, Demissie K, Vintzileos AM (2005): Trends in twin
4   II,     9.  3.  2| Smulian J, Harrigan JT, Vintzileos AM (2004): Maternal age