Hi there, http://bioperl.org/HOWTOs/Feature-Annotation/anno_from_genbank.html I am not very familiar with BioPerl. I tried to follow the example showing in the above page to retrieve pubmed ID under each Reference tag , i.e., $value->pubmed(), but it doesn't work for me for the seq gi#56961711. The authors() works for me. Appreciate any suggestions. Qunfeng