private Browser checkUserAgent(String agentString) {
		if (this.isInUserAgentString(agentString)) {
			
			if (this.children.size() > 0) {
				for (Browser childBrowser : this.children) {
					Browser match = childBrowser.checkUserAgent(agentString);
					if (match != null) { 
						return match;
					}
				}
			}
			
			// if children didn't match we continue checking the current to prevent false positives
			if (!this.containsExcludeToken(agentString)) {
				return this;
			}
			
		}
		return null;
	}