prov:value
| - Such catalysts are, for example, hydrides, oxides, hydroxides, alcoholates, amides or salts of alkali metals, such as lithium, sodium, potassium rubidium and caesium, preferably of lithium, sodium and potassium, particularly preferably of sodium and potassium (U.S. Pat. No. 3,642,858, U.S. Pat. No. 3,803,201 and EP 1082).
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