When querying for an attribute where the name contains an ampersand (&), the API returns an error.
For example, given the following query:
(Name = "O&M")
The following error is returned by WSAPI
Could not parse: Cannot parse expression "(Name = "O" as a query"
In order to query for a name attribute that contains an & you have to pre-transform it to a URL encoded character of %26
Using the above query example, change O&M to O%26M as shown below
(Name = "O%26M")