Liptobiolites occur only in the primary generation and in the early stage of the middle generation.

残植煤类仅出现在初始世代和中期世代的早期阶段。

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Mechanism of secondary hydrocarbon generation was discussed and considered to be continuous with the primary generation.

对二次生烃机理进行了讨论，认为二次生烃与一次生烃连续。

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Sustainable forms of energy can also play a key role in income generation - a primary path out of poverty for the millions who do not have access to reliable grid-distributed electricity.

BBC: Powering our way out of poverty

The final factor may sting for some up-and-coming schools without a storied tradition and history, but no one can deny that revenue generation is the primary concern for the NCAA and BCS, and certain storied programs like Notre Dame, Ohio State, USC and Alabama will sell huge numbers of tickets and bring in a tremendous amount of television advertising revenue for a BCS bowl game.

FORBES: Fixing The College Football Bowl Championship Series

Our primary investment objective is wealth preservation, but income generation does play a major role in determining our allocation.

FORBES: Investors Give Equities More Respect