Clarify "catalog"

[nickynicolson]

Line 250: it is not clear to which catalog the Authors refer to. It is important to keep in mind that authors of new taxa often do not have control on how types are treated by hosting Herbaria: the number of the voucher of the holotype may not be known at the time of publication. Likewise, the authors of new taxa do not know whether the different types (holo-, iso-) will be digitized and when.

[nickynicolson]

Add "if available"