Use of extended and prepared reference objects in experimental Fourier   transform X-ray holography
  The use of one or more gold nanoballs as reference objects for Fourier Transform holography (FTH) is analysed using experimental soft X-ray diffraction from objects consisting of separated clusters of these balls. The holograms are deconvoluted against ball reference objects to invert to images, in combination with a Wiener filter to control noise. A resolution of ~30nm, smaller than one ball, is obtained even if a large cluster of balls is used as the reference, giving the best resolution yet obtained by X-ray FTH. Methods of dealing with missing data due to a beamstop are discussed. Practical prepared objects which satisfy the FTH condition are suggested, and methods of forming them described. 
H. He, M. Howells, S. Marchesini, H. N. Chapman, U. Weierstall, H. A.   Padmore, & J. C. H. Spence