Some useful references on the topic

Badache-Damiani, C., Rozelot, J.P., Apparent solar diameter variability: a new

statistical approach to astrolabe muti-site observations, MNRAS, 2006. 369, 83-88

Boscardin, S.C., A.H. Andrei, J.L. Penna, E.G. Jilinski, and E. Reis Neto, Solar diameter variations in 2001/2002, Bulletin of the Astronomical Society of Brazil, 23, 50-50, 2003.

Dziembowski, W.A., P.R. Goode, M.P. Di Mauro, A.G. Kosovichev, and J. Schou, Solar Asymmetries from SOHO/MDI Splitting Data, in Structure and Dynamics of the Interior of the Sun and Sun-like Stars SOHO 6/GONG 98 Workshop Abstract, June 1-4, 1998, Boston, Massachusetts, p. 887, pp. 887, 1998.

Emilio, M., J.R. Kuhn, R.I. Bush, and P. Scherrer, MDI-SOHO Measures of Solar Radius Variation, in IAU Symposium 203, pp. 101, 2001.

Emilio, M., N. Leister, J. Kuhn, R. Bush, and P. Benevides-Soares, Solar radius variations over the solar cycle: ground and space experiments, in COSPAR, Plenary Meeting, pp. 2798, 2002.

Emilio, M., R. I. Bush, J. Kuhn, and P. Scherrer, A changing solar shape, The Astrophysical Journal, 660: L161–L163, 2007

Haberreiter, M., W. Schmutz and A. G. Kosovichev, Solving the discrepancy between the seismic and photospheric solar radius, The Astrophysical Journal, 675: L53–L56, 2008

Kuhn, J.R., R. Bush, M. Emilio, and P. Scherrer, On the Constancy of the Solar Diameter, American Astronomical Society Meeting Abstracts, 204, 2004a.

Kuhn, J.R., R.I. Bush, M. Emilio, and P.H. Scherrer, On the Constancy of the Solar Diameter. II., Astrophysical Journal, 613, 1241-1252, 2004b.

Laclare, F., C. Delmas, J.P. Coin, and A. Irbah, Measurements and Variations of the Solar Diameter, Solar Physics, 166, 211-229, 1996.

Lefebvre, S., and A.G. Kosovichev, Changes in the Subsurface Stratification of the Sun with the 11-Year Activity Cycle, Astrophysical Journal, 633, L149-L152, 2005.

Pap, J.M., J.R. Kuhn, Ulrich, R., Jones, A. and Rozelot, J.P., Importance of monitoring solar global properties, luminosity, radius and oscillations, in A crossroad for European Solar & Heliospheric Physics, ESA SP-417, 267-271, 1998

Penna, J.L., A.H. Andrei, S.C. Boscardin, E.G. Jilinski, E. Reis Neto, and V.A. D'Avilla, Solar Diameter Observations around the maximum of Cycle 23, in Astronomy in Latin America, pp. 171-171, 2003.

Pireaux, S., S. Lefebvre, and J.-P. Rozelot, Solar gravitational moments and solar core dynamics, in SF2A-2005: Semaine de l'Astrophysique Francaise, pp. 121, 2005.

Rozelot, J.-P., The Sun's Surface and Subsurface: Investigating Shape, LNP Vol. 599: The Sun's Surface and Subsurface: Investigating Shape, 599, 2003.

Rozelot, J.P., and S. Lefebvre, Limb shape observations at the Pic du Midi Observatory. Determination of the solar gravitational moments, in SF2A-2003: Semaine de l'Astrophysique Francaise, pp. 107, 2003.

Rozelot, J.-P., S. Lefebvre, and V. Desnoux, High-Angular Resolution Observations of the Solar Limb Shape at the Pic-du-Midi Observatory, in ASP Conf. Ser. 286: Current Theoretical Models and Future High Resolution Solar Observations: Preparing for ATST, pp. 85, 2003a.

Rozelot, J.-P., S. Lefebvre, and V. Desnoux, Observations of the Solar Limb Shape Distortions, Solar Physics, 217, 39-52, 2003b.

Rozelot, J.P., and the help of the ISSI team (namely A. Bianda, C. Damiani, N. Kilifarska, A. Kosovichev, J. Kuhn, S. Lefebvre and S. Turck-Chièze). What’s coming: issues raised from observation of the shape of the Sun. In " The rotation of the Sun and stars", Lecture Notes in Physics, LNP765, Rozelot, J.P. and Neiner, C. editors, Springer. In press.

Rozelot, J.P., Pireaux, S., Damiani, C., Kosovichev, A.K and Lefebvre, S. Probing the solar sub-surface: the leptocline and its physical properties. To be published in the proceedings of the 1rst Middle East-Africal Regional IAU meeting, Cairo (Egypt), April 2008.

Rozelot, J.P., Damiani, C., Kosovichev, A.K and Lefebvre, S., Variability of the solar shape. EGU Spring meeting, Vienna, 2008, JASTP, submitted.

Schou, J., A.G. Kosovichev, P.R. Goode, and W.A. Dziembowski, Determination of the Sun's Seismic Radius from the SOHO Michelson Doppler Imager, Astrophysical Journal, 489, L197, 1997.