Simplify the following text for a Grade 5 native English-speaking person.
Original: Poems attributed to this 5th century monarch are included in the ManyÅ shÅ `` , and a number of his verses are preserved in the Kojiki and the Nihonshoki .
Simplified: Poems that are said to be YÅ `` ryaku 's are included in the ManyÅ shÅ `` . A number of his verses are kept in the Kojiki and the Nihonshoki .