McCarthy, VN and Jordan, KD (2006) Structure and stability of the (H<inf>2</inf>O)<inf>21</inf> and (H<inf>2</inf>O)<inf>20</inf> ยท (H<inf>2</inf>S) clusters: Relevance of cluster systems to gas hydrate formation. Chemical Physics Letters, 429 (1-3). 166 - 168. ISSN 0009-2614