前面两位老师的分析很好，对初学者是很好的建议。关于make a reference 和make reference那个才是对的。补充分析如下：

▲英语通常是说 make a reference（提及），即这里的reference 用作可数名词——要么有不定冠词，要么用复数，有时也用 any, a few, some, no 等修饰（值得注意的是，为了更清楚地表明是“如何”提及某事的，这类用法这类用法中的 reference 前通常是有修饰语的，你的例子中的 penis 即是此类修饰语，只是过于粗俗而已）。如：

make an indirect reference to sth 间接提及某事；暗示某事

He made no reference to any agreement. 他没有提到什么协议。

He made oblique references to her lack of experience. 他拐弯抹角地说她缺乏经验。

She made some pointed references to his careless work. 她明确指出他工作粗心大意。

He made only a passing reference to her achievements. 他仅仅顺便提及了她的成就。

He made pointed references to the recent scandal. 他有针对性地提到最近的丑闻。

No direct reference was made to the call by the Foreign Office minister. 没有直接提及外交部长的拜访。

The article made no reference to previous research on the subject. 文章没有提及这个课题以前的研究。

She made several oblique references to the current financial situation. 她好几次拐弯抹角地提及目前的财务状况。

He made only a veiled reference to international concerns over human rights issues. 他只是含蓄地提及对人权问题的国际关注。

The governor made only a passing reference to the problem of unemployment. 州长对失业问题只是一语带过。

▲但偶尔也可见到将 reference 用作不可数名词的例子。如：

She made reference to our agreement.

He made reference to the enormous power of the mass media.