In 1999 the British botanical historian David Mabberley, in response to Meijer's findings, attempted to rescue Brown's names from synonymy. This is known as 'conservation' in taxonomy, and normally this requires making a formal proposal to the committee of the International Code of Botanical Nomenclature (ICBN). Mabberley thought he found a loophole around such a formal review by noting that while Brown was notoriously slow to get his papers published, he often had a handful of pre-print pages privately printed to exchange with other botanists: one of these pre-prints had been recently bought by the Hortus Botanicus Leiden, and it was dated April 1821. Mabberley thus proposed that this document be considered the official "effective publication", stating this would invalidate Jack's earlier name. For some reason Mabberley uses 1821, a few months after Brown's pre-print, as the date of Jack's publication, instead of the 1820 publication date in Singapore. Confusingly, the record in the International Plant Names Index (IPNI) still has yet another date, "1823?", as it was in the "Index Kewensis" before Meijer's 1997 work. Mabberley's proposals regarding Brown's name were accepted by institutions, such as the "Index Kewensis".