"How comets were assembled". University of Bern via Phys.org. 29 May 2015. Dicapai pada 8 Januari 2016. Italic or bold markup not allowed in: |publisher= (bantuan)
"How comets were assembled". University of Bern via Phys.org. 29 May 2015. Dicapai pada 8 Januari 2016. Italic or bold markup not allowed in: |publisher= (bantuan)