This site here pretty much sums up everything else you will find on this page:
Here is a collection of writings that show observable differences in the brains of people who were, and are transgender ((some of these are post-mortem studies)) (thanks to reddit user mkusanagi for this list found here; http://www.reddit.com/r/ask_transgender/comments/28rozb/what_are_some_legitimate_gender_identity_theories/)
- Jiang-Ning Zhou et al., A sex difference in the human brain and its relation to transsexuality, 378 , Published online: 02 November 1995; | doi:10.1038/378068a0 68–70 (1995)
- Milton Diamond, Biased-Interaction Theory of Psychosexual Development: “How Does One Know if One is Male or Female?,” 55 Sex Roles 589–600 (2006)
- H. E H. Pol et al., Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure, 155 European Journal of Endocrinology S107–S114 (2006)
- Kenneth J. Zucker & Anne A. Lawrence, Epidemiology of Gender Identity Disorder: Recommendations for the Standards of Care of the World Professional Association for Transgender Health, 11 International Journal of Transgenderism 8–18 (2009)
- Heino Meyer-Bahlburg, From Mental Disorder to Iatrogenic Hypogonadism: Dilemmas in Conceptualizing Gender Identity Variants as Psychiatric Conditions, 39 Archives of Sexual Behavior 461–476 (2010)
- David L. Rowland & Luca Incrocci, Handbook of Sexual and Gender Identity Disorders (John Wiley & Sons) (2008)
- Melanie Blackless et al., How sexually dimorphic are we? Review and synthesis, 12 American Journal of Human Biology 151–166 (2000)
- Frank P. M. Kruijver et al., Male-to-Female Transsexuals Have Female Neuron Numbers in a Limbic Nucleus, 85 Journal of Clinical Endocrinology & Metabolism 2034–2041 (2000)
- H. Berglund et al., Male-to-Female Transsexuals Show Sex-Atypical Hypothalamus Activation When Smelling Odorous Steroids, 18 Cerebral Cortex 1900–1908 (2008)
- Sonja Schöning et al., Neuroimaging differences in spatial cognition between men and male-to-female transsexuals before and during hormone therapy, 7 The journal of sexual medicine 1858–1867 (2010)
- Eileen Luders et al., Regional gray matter variation in male-to-female transsexualism, 46 NeuroImage 904–907 (2009)
- Sheri A. Berenbaum & Adriene M. Beltz, Sexual differentiation of human behavior: Effects of prenatal and pubertal organizational hormones, 32 Frontiers in Neuroendocrinology 183–200 (2011)
- D F Swaab, Sexual differentiation of the human brain: relevance for gender identity, transsexualism and sexual orientation, 19 Gynecological endocrinology: the official journal of the International Society of Gynecological Endocrinology 301–312 (2004)
- Alicia Garcia-Falgueras & Dick F Swaab, Sexual hormones and the brain: an essential alliance for sexual identity and sexual orientation, 17 Endocrine development 22–35 (2010)
- PENTTI K. SIITERI & JEAN D. WILSON, Testosterone formation and metabolism during male sexual differentiation in the human embryo, 38 Journal of Clinical Endocrinology & Metabolism 113–125 (1974)
- Giuseppina Rametti et al., The microstructure of white matter in male to female transsexuals before cross-sex hormonal treatment. A DTI study, 45 Journal of Psychiatric Research 949–954 (2011)
- Damian G. Zuloaga et al., The Role of Androgen Receptors in the Masculinization of Brain and Behavior: What we’ve learned from the Testicular Feminization Mutation, 53 Hormones and behavior 613–626 (2008)
- P.T Cohen-Kettenis & L.J.G Gooren, Transsexualism: A review of etiology, diagnosis and treatment, 46 Journal of Psychosomatic Research 315–333 (1999)
Here are some links for those curious about finding out more information.
Princeton on Digit Ratio
Wikipedia (take it as you will, articles here can be written by pretty much anyone)
Stamford professor explaining the dimorphisms in the brain (start @ 1:23:51):
“Transsexual gene link identified”
A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity.
Male-to-female transsexuals have female neuron numbers in a limbic nucleus.
A sex difference in the human brain and its relation to transsexuality.
Neuroimaging differences in spatial cognition between men and male-to-female transsexuals before and during hormone therapy.
Regional gray matter variation in male-to-female transsexualism.
Specific cerebral activation due to visual erotic stimuli in male-to-female transsexuals compared with male and female controls: an fMRI study.
Regional cerebral blood flow changes in female to male gender identity disorder.
ORIGINAL RESEARCH—INTERSEX AND GENDER IDENTITY DISORDERS: Neuroimaging Differences in Spatial Cognition between Men and Male-to-Female Transsexuals Before and During Hormone Therapy