/// <summary>
        /// Begin get publications file (async).
        /// Sends the request to all the sub-services in parallel. First successful response is used. Request fails only if all the sub-services fail.
        /// </summary>
        /// <param name="callback">callback when publications file is downloaded</param>
        /// <param name="asyncState">callback async state object</param>
        /// <returns>async result</returns>
        public IAsyncResult BeginGetPublicationsFile(AsyncCallback callback, object asyncState)
        {
            if (PublicationsFileService == null)
            {
                throw new HAKsiServiceException("Publications file service is missing.");
            }

            return(PublicationsFileService.BeginGetPublicationsFile(callback, asyncState));
        }