1Ghael S P, Sayeed A M, Baraink R G. Improved Wavelet Denoising Via Empirical Wiener Filtering[ J ]. In Proc. of SPIE, 1997,3169:389 - 399.
2Tu C H, Con'y M. E-learning Co,nmunities [ J ]. Quarterly Review of Distance Education, 2002 (2) :207 -218.
3Carabajal K, LaPointe D, Gunawardena C N. Group De- velopment in Online Learning Communities [ C ]//Moore M, Anderson W G. Handbook of Distance Education. N J: Lawrence Erlbaum Associates, 2003:217 - 234.
4Kickmeier-Rust D M, Albert D. The ELEKTRA Ontology Model: A Learner-Centered Approach to Resource Descrip- tion. In Proc. of ICWL, 2007:78-89.