1. INTRODUCTION

2. OBSERVATIONS AND DATA REDUCTION

3. RESULTS

4. DISCUSSION

4.1. Temperature Determination of the Dense Molecular Gas

4.2. $H_{2}O$ Masers

4.3. CH₃OH Masers

5. THE NATURE OF GALAXY NUCLEI FROM SWAN

5.1. Heating and Cooling Balance

5.2. Maser Luminosities and Star Formation

6. SUMMARY