Hi, I'd like to know if you can help me with a little issue. When I use \Rightarrow sequence, or any related sequence (\Leftrightarrow, \Longrightarrow, \iff), and compile using pdflatex, I get a colon (:) instead the desired arrow. This doesn't occur when using \Leftarrow, or \to. I'll appreciate any help or suggestion. Best wishes, Rodrigo.