Duncan, Martin J.; Quinn, Thomas; Tremaine, Scott (1987). The Formation and Extent of the Solar System Comet Cloud. The Astronomical Journal. 94: 1330. Bibcode:1987AJ.....94.1330D. doi:10.1086/114571.
Hills, Jack G. (1981). Comet showers and the steady-state infall of comets from the Oort Cloud. Astronomical Journal. 86: 1730—1740. Bibcode:1981AJ.....86.1730H. doi:10.1086/113058.
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Duncan, Martin J.; Quinn, Thomas; Tremaine, Scott (1987). The Formation and Extent of the Solar System Comet Cloud. The Astronomical Journal. 94: 1330. Bibcode:1987AJ.....94.1330D. doi:10.1086/114571.
Hills, Jack G. (1981). Comet showers and the steady-state infall of comets from the Oort Cloud. Astronomical Journal. 86: 1730—1740. Bibcode:1981AJ.....86.1730H. doi:10.1086/113058.