styles multiple inheritance

Styles do not support multiple inheritance (at least not as of Android 3.2).

The official docs say:

If you use the dot notation to extend a style, and you also include the parent attribute, then the parent styles override any styles inheritted through the dot notation.

You can only inherit one style. However, you can also make the inherited style inherit from another style, and so on:

<style name="WidgetTextBase">
    <item name="android:typeface">serif</item>
    <item name="android:textSize">12dip</item>
    <item name="android:gravity">center</item>
</style>

<style name="WidgetTextHeader" parent="WidgetTextBase">
    <item name="android:textStyle">bold</item>
</style>

<style name="BOSText" parent="WidgetTextHeader">
    <item name="android:textColor">#051C43</item>
</style>

You can't inherit more than one style, but you can set up an inheritance chain.