I obtained a Bachelor Degree in Statistics in 1988. I was separated form this profession for more than 17 years because I was exercising Information Technology. Now I returned to Statistics and an revising the Statistics and Mathematics courses of my undergraduate study in order to revive my knowledge obtaind then. I have been searching in vain for a textbook of Time Series Analysis with mathematical rigour. I want to buy a book with proves and in which the association of formulas is shown by derivation. Is there anybody who knows such a book of Time Series Analysis and can recommend me? Thank you in advance for the trouble you take to help me.