import re
 
df_tpdownloads = [" and training requirements for selected salt applications",
				  "december 31",
				  "experimental system for salt in an emergence research and applications in process heat"]
 
#for pubtitle in df_tpdownloads['PublicationTitleSplit']:
for pubtitle in df_tpdownloads:
	result = list(filter(None, re.split(r'\s*\b\w{1,3}\b\s*|[^\w\s]+', pubtitle.strip().lower())))
	print(result)
 
 
# => ['training requirements', 'selected salt applications']
# => ['december']
# => ['experimental system', 'salt', 'emergence research', 'applications', 'process heat']

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