The record derives from WCSP (in review) (data supplied on ) which reports it as a synonym and as an illegitimate name with original publication details: Nat. Hist. Bull. Siam Soc. 25: 38 1974 publ. 1975.
Full publication details for this name can be found in IPNI:
This name record (from WCSP (in review)) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Litsea pseudoelongata in version 1 of The Plant List.