hi Karolina, Here are two books that would be useful to buy. The first one has what seems to be the first statement of the "nothing-can-be-bigger-than-the-Universe" argument in terms of density perturbations. Apparently, the first scientist(s) to state the argument were not Starobinsky (1993) and Stevens et al (1993), but rather... a Polish physicist: Leopold Infeld in 1949! The second book synthesises recent papers on the Einstein-equation exact-solution approach to what i have repeatedly said in our cosmology group several times (and Helena is working on this :). In simple words: "the simplest explanation for dark energy may be the failure to do the maths carefully enough". (1) Albert Einstein: philosopher-scientist, edited by Paul Arthur Schilpp , 1949 (republished 1970) e.g. http://searchworks.stanford.edu/view/1066168 http://www.questia.com/library/book/albert-einstein-philosopher-scientist-by... (2) Bolejko et al 2009: Title: Structures in the Universe by Exact Methods Author: Krzysztof Bolejko, Andrzej Krasinski, Charles Hellaby, Marie-Noelle Celerier ISBN: 9780521769143 http://assets.cambridge.org/assets/bookpageresult.jsf?conversationId=1165892 The first book is apparently cheap, the second one expensive. Both would be useful IMHO. pozdr boud