How to use external libraries in EP

Hi!

I am with dificulties in utilizing an external ".jar" file in a Portal application (JSPDynPage). The ".jar" file is the JSTL 1.0 version. It compiles and is exported correctly (SNDS to Portal), but give me an error at runtime (NullPointerException). There is any restrictions in utilizing external ".jar"s files, e.g., not especific/proprietary versions?

Regards,

Alex