import re
test_string = "refer- ences har- ness Stand- ard Re- quired www.mypo- rtal.test.com This - is a document"
print(re.sub(r"(?<!\s)-\s+|", "", test_string))
aW1wb3J0IHJlCnRlc3Rfc3RyaW5nID0gInJlZmVyLSBlbmNlcyBoYXItIG5lc3MgU3RhbmQtIGFyZCBSZS0gcXVpcmVkIHd3dy5teXBvLSBydGFsLnRlc3QuY29tIFRoaXMgLSBpcyBhIGRvY3VtZW50IgpwcmludChyZS5zdWIociIoPzwhXHMpLVxzK3wiLCAiIiwgdGVzdF9zdHJpbmcpKQ==