Simplify the following text for a Grade 9 native English-speaking person.
Original: The few unrelated asteroids that have been found are all small ( Florczak et al 1998 , and also by inspection of the PDS asteroid taxonomy data set for non S-type members . )
Simplified: The few interlopers that have been identified are all small ( Florczak et al . 1998 , and also by inspection of the PDS asteroid taxonomy data set for non S-type members . )