Three private equity firms have offered as much as 3.5 billion euros for Springer Science, but the company's owners - Swedish private equity firm EQT and the Government of Singapore Investment Corporation (GIC) - are holding out for more, two people familiar with Springer Science's thinking told Reuters.

The people said EQT and GIC would decide on those offers within two weeks.

For now, the company said it was pressing ahead with the plan to join the stock market in Frankfurt (>> Deutsche Boerse AG) before the European summer break, selling new shares to the public to pay down debt. The two people with knowledge of the situation said the listing was planned for the first week of July.

That plan could be cancelled, even at the last minute, if an outright sale of the company is agreed.

"There is no final decision yet," said one of the people. "They are still hoping for a last-minute knock-out bid."

Springer Science's shareholders declined to comment on the sale process.

The company said it had appointed Goldman Sachs (>> Goldman Sachs Group, Inc.) and JP Morgan (>> JPMorgan Chase & Co.) as joint global coordinators and joint bookrunners. The offering includes a so-called greenshoe option, which would allow the underwriters to sell additional shares representing up to 15 percent of the offer size if there is strong demand.

These extra shares would be existing stock provided by EQT and GIC, which will not be selling shares as part of the main offering as they intend to retain a majority stake.

Springer Science publishes 2,200 English-language journals and more than 8,000 new book titles every year across five main fields that include science, business, and transport.

It competes with Anglo-Dutch publisher Reed Elsevier (>> Reed Elsevier plc) and Dutch company Wolters Kluwer (>> WOLTERS KLUWER).

Shares in those companies trade respectively at an enterprise value of 9.6 and 7.3 times expected core earnings, according to Thomson Reuters Starmine data. This would indicate a valuation of 2.5-3.3 billion euros for Springer Science.

British private equity investors Candover and Cinven created Springer Science+Business Media in 2004 by merging Dutch group Kluwer Academic Publishers with German firm BertelsmannSpringer.

In 2009, EQT and GIC bought 82 percent and 18 percent of the company respectively from Candover and Cinven.

In 2012, Springer Science's sales grew by almost 12 percent to 976.3 million euros, while adjusted earnings before interest, tax, depreciation and amortisation (EBITDA) increased by 12 percent to 343.7 million euros.

Its announcement comes days after Kion Group , the world's second-biggest forklift truck maker, said was preparing a stock market flotation in Frankfurt, hoping to take advantage of a buoyant market.

(Additional reporting by Christoph Steitz, Harro ten Wolde and Kylie MacLellan; editing by Peter Dinkloh and Tom Pfeiffer)

By Alexander Hübner and Philipp Halstrick