Task: Question Answering
Input (English): Sentence: Seattle annually sends a team of spoken word slammers to the National Poetry Slam and considers itself home to such performance poets as Buddy Wakefield, two-time Individual World Poetry Slam Champ; Anis Mojgani, two-time National Poetry Slam Champ; and Danny Sherrard, 2007 National Poetry Slam Champ and 2008 Individual World Poetry Slam Champ. Seattle also hosted the 2001 national Poetry Slam Tournament. The Seattle Poetry Festival is a biennial poetry festival that (launched first as the Poetry Circus in 1997) has featured local, regional, national, and international names in poetry. 
Question: How often is the Seattle Poetry festival held?
Output (English): biennial