Getting linking errors when running C project in VS 2010 Professional on Windows

Getting linking errors when running C project in VS 2010 Professional on
Windows

I am getting errors of the following type :
1>authenticate.obj : error LNK2001: unresolved external symbol
_ldap_first_attribute@12
1>authenticate.obj : error LNK2001: unresolved external symbol
_ldap_first_attribute@12
1>authenticate.obj : error LNK2001: unresolved external symbol
_ldap_value_free@4
1>authenticate.obj : error LNK2001: unresolved external symbol
_ldap_err2string@4
I have already added the header file folder to Project ->
Properties->C/C++->General->Additional Include Directories.
Any ideas